#include<stdio.h>

int main(){
  int a,b,c,d;
  int turn=0;
  scanf("%d%d%d%d",&a,&b,&c,&d);
  while(a==0 || c==0){
    c-=b;
    turn++;
    if(c==0)
      break;
    a-=d;
    turn++;
    if(a==0)
      break;
  }
  
  if(turn%2!=0)
    printf("Yes");
  else
    printf("No");
}