#include <iostream>
using namespace std;

#define NMax  100000000

long long memo[NMax], n, result;

long long fibbo(long long n, long long memo[])
{
  if(memo[n])
    return memo[n];
  if(n == 1 || n == 2)
  result = 1;
  else
  result = fibbo(n-1,memo) + fibbo(n-2,memo);
  memo[n] = result;
  return result;
}

int main()
{
  cin >> n;
  cout << fibbo(n, memo);
}