#include <bits/stdc++.h>
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define RREP(i,a,b) for(int i=(a);i>=(b);i--)
#define pq priotity_queue
typedef long long ll; typedef long double ld;
using namespace std;
const int INF=1e9, MOD=1e9+7, around[]={0,1,1,-1,-1,0,-1,1,0,0};
const ld PI=abs(acos(-1)); 
string s;
set<string> st;

int main(){
	REP(i,0,3){
		cin >> s;
		if(st.count(s)){cout << s << endl; break;}
		else st.insert(s);
	}
	
	return 0;
}