#include<stdio.h>

int main(void){
  
  int A,B,C,D;
  int x,y;
  
  scanf("%d%d%d%d",&A,&B,&C,&D);
  
  x==A/D;
  y==C/B;
  
  if(x>=y)
    printf("Yes");
  
  else
    printf("No");
  
  return 0;
  
}
    
    