using namespace std;
#include <bits/stdc++.h>
#define BEGIN ios_base::sync_with_stdio(0);cin.tie(0);
#define END return EXIT_SUCCESS;
#define FOR(I,A,B) for(int (I)=(A);(I)<(B);++(I))
#define ALL(C) (C).begin(),(C).end()
inline void solve()
{
	string a,b,x,y,q,w,re;
	cin>>a>>x>>q>>b>>y>>w;
	if(x.size()==y.size()){
		if(x==y)
			re="-1";
		else
			re=(x>y?a:b);
	}else{
		re=(x.size()>y.size()?a:b);
	}
	cout<<re<<endl;
}
int main(int argc,char**argv)
{
	BEGIN
	solve();
	END
}