#include<cstdio>

#define IN "nunta.in","r",stdin
#define OUT "nunta.out","w",stdout

using namespace std;
int N ;
int V[250] , A[250] , rez[250];
void add()
{
	int i , t = 0;
	for(i = 1 ; i <= V[0] || i <= A[0] || t; ++i)
	{
		if (i > V[0]) V[i] = 0;
		if (i > A[0]) A[i] = 0;
		rez[i] = (t + V[i] + A[i]) % 10 ;
		t = (t + V[i] + A[i]) / 10;
	}
	rez[0] = i-1;
}
void schimb()
{	
	for(int i = 0 ; i <= A[0] ; ++i)
		V[i] = A[i];
	for(int i = 0 ; i<= rez[0] ; ++i)
		A[i] = rez[i];
}
int main()
{
	freopen(IN);
	freopen(OUT);
	scanf("%d",&N);
	V[0] = 1; V[1] = 1;
	A[0] = 1; A[1] = 2;
	for(int i = 3 ; i <= N ; ++i)
	{
		add();
		schimb();
	}
	for(int i = A[0] ; i >= 1 ; --i)	printf("%d",A[i]);
	printf("\n");
	return 0;
}