#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c;
  cin >> a >> b >> c;
  int z[1000];
  z[0] = a;
  z[1] = b;
  for (int i = 2; i <= c; ++i) {
    z[i] = z[i - 1] + z[i - 2];
  }
  cout << z[c];
}
