#include<iostream>
#include<string>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<functional>
#include<algorithm>
#define ms0(a) memset(a,0,sizeof(a))
#define ms1(a) memset(a,-1,sizeof(a))
#define pb(a) push_back(a)
using namespace std;
typedef __int64 ll;
const double Eps = (double)0.5;
const int M = 1e9 + 7;
const int N = 2e5 + 5;
const double PI = acos(-1.0);
//int t1[10],t2[10]
char a[25];
char asr[25];
int main()
{
    int t;
    cin >> t;
    while(t--)
    {
        cin>>a;
        int l = strlen(a);
        if(l%2)
        {
            for(int i=0;i<l/2+1;i++)
                cout<<4;
           for(int i=0;i<l/2+1;i++)
                cout<<7;
                cout<<endl;
        }
        else
        {
            int n4 =0, n7 =0;
            int ok =0;
            for(int i=0;i<l;i++)
            {
                if(a[i] != '4' && a[i]!= '7')
                {
                    if(a[i] < '4')
                    {
                        if(n4 + (l-i) < n7 || n7 + (l-i) < n4)
                        {
                             for(int i=0;i<l/2+1;i++)
                                    cout<<4;
                               for(int i=0;i<l/2+1;i++)
                                    cout<<7;
                                    cout<<endl;
                                    ok = 1;
                        }
                        else
                        {
                            //if(n4 > n7)
                            {
                                int j;
                                for(j = 0; j< l/2 - n4; j++)
                                {
                                    asr[i++] = '4';
                                }
                                for(j = 0; j<l/2 - n7; j++)
                                {
                                    asr[i++] = '7';
                                }
                                asr[i] = '\0';
                                cout<<asr<<endl;
                                ok = 1;
                            }
                        }
                    }
                    else if(a[i] > '4' && a[i] < '7')
                    {
                        asr[i] = '7';
                        n7++;
                        while((++i) < l)
                        {
                            asr[i] = '4';
                            n4++;
                        }
                        asr[i] = '\0';
                    }
                    else if(a[i] > '7')
                    {
                        int k;
                        for(k = i -1 ; k>=0 ; k--)
                        {
                            if(asr[k] == '4')
                            {
                                asr[k] = '7';
                                n4--;
                                n7++;
                                break;
                            }
                        }
                        if(k>=0)
                        {
                           // asr[i] = '4';
                           // n4++;
                            for(int j=k+1; j< i;j++)
                            {
                              if(asr[j] == '7')
                              {
                                  asr[j] = '4';
                                  n7--;
                                  n4++;
                              }
                            }
                            for(int j = i; j< l; j++)
                            {
                                asr[j] = '4';
                                n4++;
                            }
                            i = l;
                            asr[l] = '\0';
                        }
                        else
                        {
                             for(int i=0;i<l/2+1;i++)
                                    cout<<4;
                               for(int i=0;i<l/2+1;i++)
                                    cout<<7;
                                    cout<<endl;
                                    ok = 1;
                        }
                    }
                }
                else if(a[i] == '4')
                {
                    asr[i] = '4';
                    n4++;
                }
                else if(a[i] == '7')
                {
                    asr[i] ='7';
                    n7++;
                }
                if (ok) break;
            }
           // printf("%s %d %d\n",asr,n4,n7);
            if (!ok)
            {
                asr[l] = '\0';
                if(n4 == n7)
                {
                    {
                        cout<<asr<<endl;
                    }
                }
                else
                {
                    if(n4 > n7)
                    {
                        for(int i = l-1; i>=0 ;i--)
                        {
                            if(asr[i] == '4')
                            {
                                asr[i] ='7';
                                n4--;
                                n7++;
                                if(n4 == n7)
                                {
                                    cout<<asr<<endl;
                                    break;
                                }
                            }
                        }
                    }
                    else
                    {
                        int okk = 0;
                        for(int k = l-1; k>= 0; k--)
                        {
                            if(asr[k] == '7')
                            {
                                n7 --;
                            }
                            else
                            {
                                n7++;
                                n4--;
                                 if(n4 + (l-k) < n7 || n7 + (l-k) < n4)
                                 {
                                    n7--;
                                    n4++;
                                    int j;
                                    for(j = k-1; j>=0; j--)
                                    {
                                        if(asr[j] == '4')
                                        {
                                            n4--;
                                        }
                                        else
                                        {
                                            //k = j + 1;
                                            break;
                                        }
                                    }
                                    k = j + 1;
                                 }
                                 else
                                 {
                                     asr[k] = '7';
                                      for(int j =0; j< l/2 - n4; j++)
                                        asr[++k] = '4';
                                    for(int j= 0; j< l/2 - n7; j++)
                                        asr[++k] = '7';
                                    asr[++k] = '\0';
                                    cout<<asr<<endl;
                                    okk = 1;
                                 }
                            }
                        }
                        if(!okk)
                        {
                               for(int i=0;i<l/2+1;i++)
                                        cout<<4;
                                   for(int i=0;i<l/2+1;i++)
                                        cout<<7;
                                        cout<<endl;
                        }
                    }
                }
            }
        }
    }
}