#include <stdio.h>

int main()
{
    int a, b, c, d;
    scanf("%d%d%d%d", &a, &b, &c, &d);

    int i = 1;

    while(1)
    {
        if(i%2 == 1)
        {
            c -= b;

            if(c <= 0)
            {
                 printf("Yes\n");
                 break;
            }
        }

        else
        {
            a -= d;

            if(a <= 0)
            {
                 printf("No\n");
                 break;
            }
        }

        i++;
    }

    return 0;
}
