#include <iostream>

using namespace std;

int main() {
    int k;
    cin >> k;
    
    if (k == 1 || k == 2) {
        cout << 1 << endl;
        return 0;
    }
    
    long long a = 1, b = 1, c;
    for (int i = 3; i <= k; i++) {
        c = a + b;
        a = b;
        b = c;
    }
    
    cout << b << endl;
    
    return 0;
}