#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main(){
  string a, b;
  cin >> a >> b;
  ll A = 0, B = 0;
  FOR(i,0,a.length()){
    A *= 10;
    A += a[i] == '4' ? 8 : a[i] - '0';
  }
  FOR(i,0,b.length()){
    B *= 10;
    B += b[i] == '4' ? 8 : b[i] - '0';
  }
  cout << (A > B ? a : b) << endl;
  return 0;
}