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

}

/**************************************************************
	Problem: 1749
	User: mc002
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/