#include <iostream>

using namespace std;

#define LL long long
#define maxDim 105

int prez[maxDim], ant[maxDim], ult[maxDim];


void add (int a[], int b[])
{
	int i, dima = 0;
	for (i = 1; i <= a[0] || i <= b[0] || dima; ++ i)
	{
		dima += a[i] + b[i];
		a[i] = dima % 10;
		dima /= 10;
	}
	
	a[0] = i - 1;
}


int main()
{
	freopen ("nunta.in", "r", stdin);
	freopen ("nunta.out", "w", stdout);
	
	int N;
	
	scanf ("%d", &N);
	
	ult[0] = 1;
	ult[1] = 1;
	
	for (int i = 1; i <= N; ++ i)
	{
		memset (prez, 0, sizeof (prez));
		add (prez, ant);
		add (prez, ult);
		
		memset (ant, 0, sizeof (ant));
		add (ant, ult);
		
		memset (ult, 0, sizeof (ult));
		add (ult, prez);
	}
	
	
	for (int i = ult[0]; i >= 1; -- i)
		printf ("%d", ult[i]);
	
	return 0;
}