#include <bits/stdc++.h>
int q[1005];
int main() {
  int a, b, c;
  while (scanf("%d%d%d", &a, &b, &c) != EOF) {
    q[0] = a;
    q[1] = b;
    for (int i = 2; i <= c; i++) {
      q[i] = q[i - 1] + q[i - 2];
    }
    printf("%d\n", q[c]);
  }
  return 0;
}
