#include<bits/stdc++.h>
using namespace std;

int main()
{
    int a,b,c;
    cin>>a>>b>>c;
    if(a==b){
        cout<<c;
        return 0;
    }
    else if(a==c){
        cout<<b;
        return 0;
    }
    else{
        cout<<a;
        return 0;
    }
}
