#include <iostream>

using namespace std;

int main() {

    int f0 = 0, f1 = 1, f2 = 1, fn = 0;

    int n;

    cin >> n;

    switch (n) {
        case 0:
            cout << f0;
            break;
        case 1:
            cout << f1;
            break;
        case 2:
            cout << f2;
            break;
        default:
            for (int i = 0; i < n - 2; ++i)
            {
                fn = f0 + f2;
                f0 = f1;
                f1 = f2;
                f2 = fn;
            }
            cout << fn;
            break;
    }

    return 0;
}