#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001


int main(){
	
	int a,b,c;
	cin>>a>>b>>c;
	
	cout<<(a^b^c)<<endl;
	
    return 0;
}