/*#include<cstdio>
#include<cmath>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<string>
#include<stack>
#include<queue>
#include<map>
#include<utility>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
const int MN=1000000+10;
const int ME=100000+10;
const int mod=1000000007;
typedef long long LL;
typedef unsigned long long ULL;
const double pi=acos(-1.0);
const int Intmax=(~(1<<31));
const int Intmin=(1<<31);
const LL LLmax=(~(1LL<<63));
const LL LLmin=(1LL<<63);
const ULL ULLmax=(~(0ULL));
int c[123];
char s[123];
int dp[123];
int main(){
#ifndef ONLINE_JUDGE
    freopen("1.cpp","r",stdin);
#endif // ONLINE_JUDGE
    int t,k,l;
    scanf("%d",&t);
    while(t--){
        memset(c,0,sizeof(c));
        scanf("%d%d%d",&n,&k,&l);
        for(int i=0;i<n;i++){
            scanf("%s",s);
            int len=strlen(s);
            for(int j=0;j<len;j++){
                c[1]++;
                int l=1;
                while(1){
                    if(j-l>=0&&j+l<len){
                        if(s[j-l]==s[j+l])
                            c[l*2+1]++;
                        else break;
                    } else break;
                }
                if(j+1<len&&c[j]==c[j+1]){
                    c[2]++;
                    int l=1;
                    while(1){
                        if(j-l>=0&&j+1+l<len){
                            if(s[j-l]==s[j+1+l])
                                c[l*2+2]++;
                            else break;
                        } else break;
                    }
                }
            }
        }
        if(k<=c[1]&&k>=l){
            printf("True\n");
        } else {
            bool can=0;
            memset(dp,0,sizeof(dp));
            int i,j,k;
            for(i=1;i<=100;i++){
                for(j=1;j<=c[i];j*=2){
                    int v=i*j;
                    for(k=l;k>=v;k--){
                    }
                }
            }
            if(can)
            printf("True\n");
            else printf("False\n");
        }
    }
    return 0;
}
*/
#include<cstdio>
#include<cmath>
#include<iostream>
#include<cstring>
#include<algorithm>
#include<string>
#include<stack>
#include<queue>
#include<map>
#include<utility>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
const int MN=1000000+10;
const int ME=100000+10;
const int mod=1000000007;
typedef long long LL;
typedef unsigned long long ULL;
const double pi=acos(-1.0);
const int Intmax=(~(1<<31));
const int Intmin=(1<<31);
const LL LLmax=(~(1LL<<63));
const LL LLmin=(1LL<<63);
const ULL ULLmax=(~(0ULL));
int l;
char a[25];
char ans[25];
char tmp[25];
void dfs(int i,int x,bool flag){
    if(i==l){
        if(x!=l/2) return ;
        ans[i++]='\0';
        int c=strcmp(ans,a);
        int p=strcmp(ans,tmp);
        if(c>=0){
            if(p<0){
                strcpy(tmp,ans);
            }
        }
        return ;
    }
    if(flag){
            if(x<l/2){
                ans[i]='4';
                dfs(i+1,x+1,flag);
            }
            else{
                ans[i]='7';
                dfs(i+1,x,flag);
            }
    }
    else{
            if(a[i]-'0'<4){
                    ans[i]='4';
                    bool tmp=false;;
                if(ans[i]>a[i]) tmp=true;
                    dfs(i+1,x+1,tmp);
            }else if(a[i]=='4'){
                    ans[i]='4';
                    dfs(i+1,x+1,false);
                    ans[i]='7';
                    dfs(i+1,x,true);
            }else{
                ans[i]='7';
                bool tmp=false;
                if(ans[i]>a[i]) tmp=true;
                dfs(i+1,x,tmp);
            }
    }
}
int main(){
#ifndef ONLINE_JUDGE
    freopen("1.cpp","r",stdin);
#endif // ONLINE_JUDGE
    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%s",a);
        l=strlen(a);
        memset(tmp,'9',sizeof(tmp));
        tmp[24]='\0';
        if(l&1){
            l++;
            int x=l/2,y=l/2;
            while(x--){
                printf("4");
            }
            while(y--){
                printf("7");
            }
            printf("\n");
        }else{
            int i;
            LL A=0;
            LL B=0;
            for(i=0;i<l;i++){
                A*=10;
                A+=(a[i]-'0');
                B*=10;
                if(i<l/2) B+=7;
                else B+=4;
            }
            if(A>B){
                l+=2;
                int x=l/2,y=l/2;
                while(x--) printf("4");
                while(y--) printf("7");
                printf("\n");
            }
            else{
                bool flag=false;
                dfs(0,0,0);
                printf("%s\n",tmp);
            }
        }
    }
    return 0;
}