#include<cstdio>
#include<cstring>
#include<cctype>
#include<algorithm>
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define dwn(i,s,t) for(int i=s;i>=t;i--)
using namespace std;
inline int read() {
    int x=0,f=1;char c=getchar();
    for(;!isdigit(c);c=getchar()) if(c=='-') f=-1;
    for(;isdigit(c);c=getchar()) x=x*10+c-'0';
    return x*f;
}
const int maxn=10000010;
typedef long long ll;
int N,len,bit[20];
ll A[maxn];
void solve() {
    ll n;scanf("%I64d",&n);ll t=n;len=0;
    while(t) bit[++len]=t%10,t/=10;
    if(len&1) {
        rep(i,1,(len+1)/2) putchar('4');
        rep(i,1,(len+1)/2) putchar('7');
    }
    else {
        ll tmp=0;
        rep(i,1,len/2) tmp=tmp*10+7;
        rep(i,1,len/2) tmp=tmp*10+4;
        if(tmp<n) {
            rep(i,1,(len+2)/2) putchar('4');
            rep(i,1,(len+2)/2) putchar('7');
        }
        else {
            int l=1,r=N,mid;
            while(l<r) if(A[mid=l+r>>1]>=n) r=mid; else l=mid+1;
            printf("%I64d",A[l]);
        }
    }
    puts("");
}
int main() {
    rep(M,1,18) {
        rep(S,0,(1<<M)-1) {
            ll tmp=0,c=0;
            rep(i,0,M-1) 
                if(S>>i&1) tmp=tmp*10+4,c--;
                else tmp=tmp*10+7,c++;
            if(!c) A[++N]=tmp;
        }
    }
    sort(A+1,A+N+1);
    dwn(T,read(),1) solve();
    return 0;
}