#include<bits/stdc++.h>
using namespace std;
int n,a[1000];
int main()
{
	cin >> n;
	a[1] = 1;
	a[2] = 1;
	for( int i = 3; i <= n; i++)
	{
		a[i] = a[i - 1] + a[i - 2];
	}
	cout << a[n];
	return 0;
}

/**************************************************************
	Problem: 1238
	User: yangwanning
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2076 kb
****************************************************************/