#include <stdio.h>
#include <string.h>
#include <stdbool.h>

int main() {
    int a, b, c, d;
    scanf("%d %d %d %d", &a, &b, &c, &d);
    while (a > 0 && c > 0) {
        c -= b;
        if (c < 0) break;
        a -= d;
    }
    if (c == 0) printf("Yes\n");
    else printf("No\n");
}