#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cmath>
#include <string>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <sstream>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#pragma comment(linker,"/STACK:102400000,102400000")

using namespace std;
#define   MAX           100005
#define   MAXN          1000005
#define   maxnode       500005
#define   sigma_size    30
#define   lson          l,m,rt<<1
#define   rson          m+1,r,rt<<1|1
#define   lrt           rt<<1
#define   rrt           rt<<1|1
#define   middle        int m=(r+l)>>1
#define   LL            long long
#define   ull           unsigned long long
#define   mem(x,v)      memset(x,v,sizeof(x))
#define   lowbit(x)     (x&-x)
#define   pii           pair<int,int>
#define   bits(a)       __builtin_popcount(a)
#define   mk            make_pair

const int    prime = 999983;
const int    INF   = 0x3f3f3f3f;
const LL     INFF  = 1e18;
const double pi    = 3.141592653589793;
const double inf   = 1e18;
const double eps   = 1e-10;
const int    mod   = 10007;
const ull    mx    = 133333331;

/*****************************************************/
inline int read_int(){
    int ret=0;
    char tmp;
    while(!isdigit(tmp=getchar()));
    do{
        ret=(ret<<3)+(ret<<1)+tmp-'0';
    }
    while(isdigit(tmp=getchar()));
    return ret;
}
/*****************************************************/
char s[MAX];
char ss[MAX];
 int T;
bool check(char *s){
    int len=strlen(s);
    int num1=0,num2=0;
    for(int i=0;i<len;i++){
        if(s[i]=='4') num1++;
        if(s[i]=='7') num2++;
    }
    if(num1==num2&&num1+num2==len) return true;
    return false;
}

int main(){
cin>>T;
    while(T--){
            scanf("%s",s);
        if(check(s)){
            printf("%s\n",s);
            continue;
        }
        int len=strlen(s);
        if(len%2==1){
            int n=(len+1)/2;
            for(int i=0;i<n;i++) printf("4");
            for(int i=0;i<n;i++) printf("7");
            printf("\n");
        }
        else{
            int n=len/2;
            for(int i=0;i<n;i++) ss[i]='7';
            for(int i=0;i<n;i++) ss[i+n]='4';
            ss[len]=0;
            if(strcmp(ss,s)<0){
                n++;
                for(int i=0;i<n;i++) printf("4");
                for(int i=0;i<n;i++) printf("7");
                printf("\n");
            }
            else{
                int pos=0;
                int flag=0;
                int f=0;
                int n1=0,n2=0;
                for(int i=0;i<len;i++){
                    if(s[i]<'4'){
                        if(n1<n) ss[i]='4';
                        else if(n1==n) ss[i]='7';
                        flag=i+1;
                        break;
                    }
                    else if(s[i]=='4'){
                        if(n2<n) pos=i;
                        if(n1<n){
                            ss[i]='4';
                            n1++;
                        }
                        else if(n1==n){
                            ss[i]='7';
                            flag=i+1;
                            break;
                        }
                    }
                    else if(s[i]>'4'&&s[i]<'7'){
                        if(n2<n){
                            ss[i]='7';
                            flag=i+1;
                            break;
                        }
                        else if(n2==n){
                            f=1;
                            break;
                        }
                    }
                    else if(s[i]=='7'){
                        if(n2<n){
                            ss[i]='7';
                            n2++;
                        }
                        else{
                            f=1;
                            break;
                        }
                    }
                    else if(s[i]>'7'){
                        f=1;
                        break;
                    }
                }
                if(f){
                    ss[pos]='7';
                    flag=pos+1;
                }
                int num1=0,num2=0;
                for(int i=0;i<flag;i++){
                    printf("%c",ss[i]);
                    if(ss[i]=='4') num1++;
                    if(ss[i]=='7') num2++;
                }
                for(int i=0;i<n-num1;i++) printf("4");
                for(int i=0;i<n-num2;i++) printf("7");
                printf("\n");
            }
        }
    }
    return 0;
}