import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int H = sc.nextInt(); // 행
        int W = sc.nextInt(); // 열
        int N = sc.nextInt(); // 세로 거리
        int M = sc.nextInt(); // 가로 거리

        int vertical = countNum(N, H);
        int horizontal = countNum(M, W);

        System.out.println(vertical * horizontal);
    }

    private static int countNum(int distance, int length) {
        int count = 1;
        int start = 1;

        while (start < length) {
            start += distance + 1;

            if (start <= length) {
                count++;
            }
        }

        return count;
    }
}