#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    //long long mod = ;
    int a,b;
    long long t,ans=1;
    cin>>a>>b>>t;
    for(long long i=1; i<=t; i++){
        ans = ((0.5*a*ans+0.5*b*ans));
    }
    cout<<ans;
    return 0;
}