#include<bits/stdc++.h>
using namespace std;
int f(int k)//求走k级楼梯的走法数
{
    if(k <= 2)
        return k;
    return f(k-1) + f(k-2);
}
int main() 
{
    int n;
    while(cin >> n)
        cout << f(n) << endl;      
	return 0;
}