#include <iostream>
#include <math.h>
using namespace std;
#define P(x) (cout << x << endl)
int main(){
    string s1,s2,t,p1,p2;
    cin>>s1>>p1>>t>>s2>>p2;
    int f=0;
    if(p1.size() != p2.size()){
        f=1;
        if(p1.size()<p2.size()) f=2;
    }else{
        for(int i=0;i<p1.size();i++){
            if(p1[i] != p2[i]){
                f=1;
                if(p1[i] < p2[i]) f =2;
                break;
            }
        }
    }
    if(f==1) P(s1);
    else if(f==2) P(s2);
    else P("-1");
}