#include<stdio.h>
void main()
{
   int a,b,c,d,k,t;
  scanf("%d %d %d %d",&a,&b,&c,&d);
  while(1)
  {
     k=c-b;
      if(k<=0)
      {
        break;
      }
     t=a-d;
    if(t<=0)
    {
       break;
    }
  }
  if(k>t)
    printf("no");
  else
    printf("yes");
}
