#include<bits/stdc++.h>
using namespace std;

int main(){
    string sa,sb,pa,pb;
    char w;
    cin >> sa >> pa >> w;
    cin >> sb >> pb >> w;

    if(pa.size()>pb.size()) cout << sa << endl;
    else if(pa.size()<pb.size()) cout << sb << endl;
    else{
        for(int i=0;i<pa.size();i++){
            int a=pa[i]-'0',b=pb[i]-'0';
            if(a==b) continue;
            else if(a>b) cout << sa << endl;
            else cout << sb << endl;
            return 0;
        }
        cout << -1 << endl;
    }

    return 0;
}