week_2_1

#include <iostream>
#include <vector>

using namespace std;

long long fib_number(int n) {
        vector<long long> f(n);
        f[0] = 1;
        f[1] = 1;
        for (int i = 2; i < n; i++) {
                f[i] = f[i-1] + f[i-2];
        }

        return f[n-1];
}

int main() {
        int n;
        cin >> n;
        cout << fib_number(n) << endl;
}