#include <stdio.h>
int main(){
  int a,b,c,d;
  int tmp;
  scanf("%d %d %d %d",&a,&b,&c,&d);

  while(1){
    tmp= c-b;
    if(tmp<=0){
      printf("Yes\n");
      return 0;
    }
    c = tmp;
    tmp = a-d;
    if(tmp<=0){
      printf("No\n");
      return 0;
    }
    a = tmp;
  }

  return 0;
}