#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int main(){
    ll a,b,n,ans;
    cin>>a>>b>>n;
    vector<ll> f;
    f.emplace_back(a);
    f.emplace_back(b);
    for(int i=2;i<=n;++i)f.emplace_back(f[i-1]^f[i-2]);
    ans=f[n];
    cout<<ans<<endl;
}