#include<stdio.h>

int main()
{
	int fib1{ 1 }, fib2{ 1 }, n;

	scanf("%d", &n);
	for (int i = 1; i < n; ++i)
	{
		int tmp = fib2;
		fib2 += fib1;
		fib1 = tmp;
	}
	printf("%d\n", fib2);
	return 0;
}
