#include <iostream>
using namespace std;
int main()
{
    int n, i, a = 1, b = 1, c = 1;
    cin >> n;
    if ( n == 0) {
        c = 0;
    } else if ( n == 1 || n == 2){
        c = 1;
    } else {
        for ( i = 2; i<n; i++){
            c = a + b;
            a = b;
            b = c;
        }

    }
    cout << c;

}