#include <iostream>
using namespace std;

int main()
{
    int fib[50] = {1, 1};
    int n;
    cin >> n;    
    
    for(int i = 2; i <= n; ++i){
        fib[i] = fib[i-1] + fib[i-2];
    }
    cout << fib[n] << endl;
}