#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <iomanip>
#include <list>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <algorithm>
#include <numeric>
#include <functional>

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define ALL(a) (a).begin(),(a).end()

using namespace std;
typedef long long ll;

int main(int argc, char *argv[])
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  string sa, sb, pa, pb, xa, xb;
  
  cin >> sa >> pa >> xa >> sb >> pb >> xb;

  if (pa.length() > pb.length()) {
    cout << sa << endl;
    return 0;
  }
  if (pb.length() > pa.length()) {
    cout << sb << endl;
    return 0;
  }
  int L = pa.length();
  REP(i,L) {
    if (pa[i] > pb[i]) {
      cout << sa << endl;
      return 0;
    }
    if (pb[i] > pa[i]) {
      cout << sb << endl;
      return 0;
    }
  }
  cout << -1 << endl;

  return 0;
}