import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner in = new Scanner(System.in);
String str = in.nextLine();
String[] strs = str.split(" ");
int n = Integer.parseInt(strs[0]);
int h = Integer.parseInt(strs[1]);
int m = Integer.parseInt(strs[2]);
int remainder = n - (m + h - 1) / h;//喝完一盒后另一盒立即打开
System.out.println(remainder);
}
}