#include <iostream>

int8_t N;
int64_t dp1, dp2;

int main(void) {
	scanf("%hhd", &N);
	
	dp1 = 1, dp2 = 0;
	for(int8_t i = 0; i < N; ++i) {
		if(i & 1) dp1 += dp2;
		else dp2 += dp1;
	}
	
	if(N & 1) printf("%ld\n", dp2);
	else printf("%ld\n", dp1);
	return 0;
}