#include <iostream>

using namespace std;

int main()

{
    int a;
    int b;
    int c;
    cin>>a;
    cin>>b;
    cin>>c;
if (a==b){
    cout <<c;
}

else if (a==c){
    cout<<b;
}

else{
    cout<<a<<endl;
}

 return 0;
}