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