#include<stdio.h>
#include<math.h>
int main()
{
    int a;
    int b;
    int c;
    int d;
    scanf("%d %d %d %d",&a,&b,&c,&d);
    int win_a=0;
    win_a=a%d;
    int win_b=0;
    win_b=c%b;
    if(win_a<=win_b)
        printf("Yes\n");
    else 
        printf("No\n");
    return 0;
}