#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>

#include<map>
#include<set>
#include<string>
#include<algorithm>
#include<functional>
using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define INF 1<<30
#define MP make_pair
#define mp make_pair
#define pb push_back
#define PB push_back
#define DEBUG(x) cout<<#x<<": "<<x<<endl
#define ll long long
#define ull unsigned long long
bool cmp(string a,string b){
	if(a.size()>b.size()) return true;
	if(a.size()<b.size()) return false;
	if(a>b) return true;
	return false;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	string a,b;string an,bn;char t;
	cin>>a>>an>>t>>b>>bn>>t;
	if(cmp(an,bn)) cout<<a<<endl;
	else if(cmp(bn,an)) cout<<b<<endl;
	else cout<<-1<<endl;
	 

}