关于一个简单的递归

#include<stdio.h>
int F(int x)
{
	if(x==2||x==1||x==0)return 1;
	if(x>2) return F(x-1)+(x-2)+F(x-3);
}
int main(void)
{
	int y;
	scanf("%d",&y);
	printf("%d",F(y));
	return 0;
}