#include <bits/stdc++.h>
using namespace std;
  
// #define int long long
#define pb push_back
#define print(Target) cout << Target << '\n'

#define REP(i, n) for (int i = 0; i < (n); i++)
#define REPS(i, a, n) for (int i = (a); i < (n); i++)

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int> > vii;
typedef pair<int, int> pii;

bool is_uruu(int y) {return (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0));}

signed main()
{
  ios::sync_with_stdio(false);
  string s[2], p[2], x[2];
  REP(i, 2) cin >> s[i] >> p[i] >> x[i];
  bool flg = true;

  if (p[0].size() != p[1].size()){
    print(s[p[0].size() < p[1].size()]);
    flg = false;
  }else {
    REP(i, p[0].size()){
      if (p[0][i] != p[1][i]){
        print(s[p[0][i] < p[1][i]]);
        flg = false;
        break;
      }
    }
  }
  if (flg){
    print("-1");
  }

  return (0);
}