#include<stdio.h>
//遞歸和非遞歸分別實現求第n個斐波那契數
//非遞歸
int main()
{
	int i = 1;
	int j = 1;
	int temp = 0;
	int n = 0;
	int fib = 0;
	scanf("%d", &n);
	while (n > 0)
	{
		if (n > 2)
		{
			temp = j;
			j = i + j;
			i = temp;
		}
		else 
			fib = j;
		n--;
	}
	printf("%d", fib);
	return 0;
}

//遞歸
int Fib(int n)
{
	if (n > 2)
	{
		return Fib(n - 1) + Fib(n - 2);
	}
	else 
	{
		return 1;
	}
}
int main()
{
	int n = 0;
	scanf("%d", &n);
	while (1)
	{
		if (n <= 0)
		{
			printf("輸入錯誤請重新輸入:>");
		}
		else
		{
			printf("%d\n", Fib(n));
			break;
		}
	}
	return 0;
}