#include<cstdio>

using namespace std;

int N,i,j,t,A[250],B[250],C[250];

int main()
{
	freopen( "nunta.in" , "r" , stdin );
	freopen( "nunta.out" , "w" , stdout );
	scanf("%d" , &N );
	A[0] = B[0] = A[1] = 1;
	B[1] = 2;
	for( j = 3 ; j <= N ; ++j )
		{
			t = 0;
			for (i=1; i<=A[0] || i<=B[0] || t; i++, t/=10)
				C[i] = (t += A[i] + B[i]) % 10;
			C[0] = i - 1;
			for( i = 0 ; i <= C[0] ; ++i )
				{
					A[i] = B[i];
					B[i] = C[i];
				}
		}
	if( N == 1 )
		printf( "1\n" );
		else
		{
			for( i = B[0] ; i ; --i )
				printf("%d" , B[i] );
			printf( "\n" );
		}
	return 0;
}