#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    int a = 0, b = 1, c = 1;
    while (n) {
        if (n > 1) {
            c = a + b;
            a = b;
            b = c;
        }
        --n;
    }
    cout << c;
    return 0;
}