fib

#include<iostream>

using namespace std;

int main()
{
    int a = 1, b = 0;

    int n;

    cin >> n;

    for(int i = 1; i <= n; i++)
    {
        if(i % 2 == 1)
            a += b;
        else
            b += a;
    }

    if(n % 2 == 1)
        cout << a << endl;
    else
        cout << b << endl;
}