#include <bits/stdc++.h>
#define PB push_back
#define MP make_pair
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(),(a).end()
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
const int INF=1e9;
const int MOD=100000;
int B=1000000;
int com(string a,string b){
      if(a.size()>b.size())return 1;
      else if(a.size()<b.size())return 2;
      REP(i,a.size()){
            if(a[i]==b[i])continue;
            if(a[i]>b[i])return 1;
            if(a[i]<b[i])return 2;
      }
      return -1;
}
int main(){
      string s[2],p[2];
      char c[2];
      REP(i,2)cin>>s[i]>>p[i]>>c[i];
      int f=com(p[0],p[1]);
      if(f==1){
            cout<<s[0]<<endl;
      }else if(f==2){
            cout<<s[1]<<endl;
      }else cout<<-1<<endl;
      return 0;
}