#include <bits/stdc++.h>

int main() {

  long dp[64];
  long N;

  dp[0] = 1;
  dp[1] = 1;
  for(int i = 2; i < 64; ++i) {
    dp[i] = dp[i-1] + dp[i-2];
  }

  std::cin >> N;
  std::cout << dp[N] << std::endl;
  
  return 0;
}