#include<iostream>
#include<cstdio>

using namespace std;

int f(int n)
{
    if (n == 1) return 1;
    if (n == 2) return 1;
    return f(n - 1) + f(n - 2);
}

int main()
{
    int n;
    scanf("%d", &n);

    int x = f(n);
    printf("%d\n", x);
    return 0;
}