#include<stdio.h>
int main()
{
	int i,n,c=0;
	scanf("%d",&n);
	for(i=1900;i<=n;i++)
	{
		if((i%4==0&&i%100!=0)||(i%400==0)) c++;
	}
	printf("%d",c);
	return 0;
}
/**************************************************************
	Problem: 1749
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/