#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cstdio>
using namespace std;
int main(){
    string s1,s2,a1,a2;
    char none;
    bool flag;
    flag = true;
    cin >> s1 >> a1 >> none >> s2 >> a2 >> none;
    if(a1.size()==a2.size()){
        flag = false;
        for(int i=0;i<a1.size();i++){
            if(a1[i]<a2[i]){
                cout << s2;
                flag = true;
                break;
            }
            else if(a1[i]>a2[i]){
                cout << s1;
                flag = true;
                break;
            }
        }
    }
    else if(a1.size()>a2.size()){
        cout << s1;
    }
    else{
        cout << s2;
    }
    if(flag==false)   cout << -1;
    return 0;
}