#include<iostream>

using namespace std;
	
int gj[1001] = { 1 }, last[1001] = { 2 }, len = 1;

int main( ) {
	
	int n; cin >> n;
	
	if ( n == 1 ) {
		cout << 1;
		return 0;
	} if ( n == 2 ) {
		cout << 2;
		return 0;
	}
	
	for ( int i = 3; i <= n; i++ ) {
		for ( int j = 0; j < len; j++ )
			gj[j] += last[j], gj[j+1] += gj[j] / 10, gj[j] %= 10;
		if ( gj[len] )
			len++;
		
		swap( gj, last );
	}
	
	for ( int i = len - 1; i >= 0; i-- )
		cout << last[i];
		
	return 0;
		 
}