#include <stdio.h>

int aStr, aHp, bStr, bHp;

int main() {

    scanf("%d %d %d %d", &aHp, &aStr, &bHp, &bStr);

    while (1) {
        bHp -= aStr;
        if (bHp <= 0) {
            printf("Yes\n");
            break;
        }

        aHp -= bStr;
        if (aHp <= 0) {
            printf("No\n");
            break;
        }
    }

    return 0;
}