#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define all(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  string Sa,Xa,Sb,Xb;
  string Pa,Pb;
  cin >> Sa >> Pa >> Xa;
  cin >> Sb >> Pb >> Xb;
  if(Pa.size() > Pb.size()){
  	cout << Sa << endl;
  }
  else if(Pa.size() < Pb.size()){
  	cout << Sb << endl;
  }
  else{
  	if(Pa == Pb){
  		cout << -1 << endl;
  		return 0;
  	}
  	for(int i=0;i<Pa.size();++i){
  		if(Pa[i] > Pb[i]){
  			cout << Sa << endl;
  			break;
  		}
  		if(Pa[i] < Pb[i]){
  			cout << Sb << endl;
  			break;
  		}
  	}
  }
  return 0;
}