#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n,cnt=0;
	cin>>n;
	for(int i=1900;i<=n;i++)
	{
		if(i%4==0&&i%100!=0||i%400==0)
		{
			cnt++;
		}	
	} 
	cout<<cnt;
	return 0;
}

/**************************************************************
	Problem: 1749
	User: lzc
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/