#include<stdio.h>
int main(void){
	int a,b,c,d;
  int t = 1;
  int x;
  int h;
  scanf("%d %d %d %d",&a,&b,&c,&d);
  while(t != 0){
    	t = c - b;
    	h = a - d;
  }
  if(t < h){
    printf("No");
  }else{
    printf("Yes");
  }
  return 0;
}
   		
  