#include<stdio.h>
void main()
{
 int a,b,c,d,i=1;
 scanf("%d",&a);
 scanf("%d",&b);
 scanf("%d",&c);
 scanf("%d",&d);
while(a>0 && c>0)
{
 if(i%2==1)
 {
    c=c-b;
 }
  else
 { 
     a=a-d;
 }
 i++;
} 
if(a<=0)
 printf("No");
else
 printf("Yes");
}