#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  int f[c + 1];
  f[0] = a;
  f[1] = b;
  for (int i = 2; i <= c; ++i) f[i] = f[i - 1] + f[i - 2];
  cout << f[c] << endl;
  return 0;
}
