#include <stdio.h>

int fib(int n) {
	if(n == 0)
	return 0;
	else if(n == 1)
	return 1;
	else
	return fib(n - 1) + fib(n - 2);
}

int main(void) {
	int n;
	scanf("%d", &n);
	printf("%d", fib(n));
	return 0;
}