#include <stdio.h>
#include <float.h>

int main()
{
    long int takahashi_life, takahashi_power, aoki_life, aoki_power;
    scanf("%ld %ld %ld %ld", &takahashi_life, &takahashi_power, &aoki_life, &aoki_power);

    while(1)
    {
        aoki_life -= takahashi_power;
        if(aoki_life <= 0)
        {
            printf("Yes\n");
            break;
        }
        takahashi_life -= aoki_power;
        if(takahashi_life <= 0)
        {
            printf("No\n");
            break;
        }
    }

    return 0;
}


