#include<stdio.h>

int main(){
  int a,b,c,d;
  float x,y;
  scanf("%d%d%d%d",&a,&b,&c,&d);
  x=a/d; y=c/b;
  if(x<y)
    printf("Yes");
  else if(x>y)
    printf("No");
  else if(x==y)
    printf("Yes");
}