#include<stdio.h>

int attack(int hp, int at) {
    hp -= at;
    return hp;
}

int main() {
    int taka_hp, taka_at;
    int aoki_hp, aoki_at;
    scanf("%d %d %d %d", &taka_hp, &taka_at, &aoki_hp, &aoki_at);
    while(1) {
        aoki_hp = attack(aoki_hp, taka_at);
        if(aoki_hp <= 0) {
            printf("Yes\n");
            break;
        }
        taka_hp = attack(taka_hp, aoki_at);
        if(taka_hp <= 0) {
            printf("No\n");
            break;
        }
    }
}
