#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int mcomp(string s1, string s2) {
  if (s1.size() != s2.size()) {
    if (s1.size() > s2.size()) {
      return 0;
    }else {
      return 1;
    }
  }else {
    for (int i = 0; i < s1.size(); i++) {
      if (s1[i]-'0' > s2[i]-'0') {
	return 0;
      }else if (s1[i]-'0' < s2[i]-'0') {
	return 1;
      }
    }
  }
  return -1;
}

int main() {
  string sa, sb;
  string pa, pb;
  string xa, xb;
  cin >> sa >> pa >> xa;
  cin >> sb >> pb >> xb;
  if (mcomp(pa, pb) == 0) {
    std::cout << sa << std::endl;
  }else if (mcomp(pa, pb) == 1) {
    std::cout << sb << std::endl;
  }else {
    std::cout << -1 << std::endl;
  }
}