#include <iostream>
using namespace std;

int main(){
	int i,n,c = 0;
	cin>>n;
	for(i = 1900;i <= n;i++){
		if(i%4==0&&i%100!=0 || i % 400==0){
//			cout<<i<<endl;
			c++;
		}
	}
	cout<<c;
}
/**************************************************************
	Problem: 1749
	User: admin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/