import java.util.Scanner;

public class Main{

public static void main(String[] agrs){

Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int s = 0;
for(int i = 1900;i <= n;i++){
		
		if((i % 4 == 0 && i % 100 != 0) || (i % 400 == 0)){
		s++;
		}
}System.out.println(s);
}
}
/**************************************************************
	Problem: 1749
	User: admin
	Language: Java
	Result: Accepted
	Time:723 ms
	Memory:40076 kb
****************************************************************/