#include <stdio.h>

int main()
{
 int A,B,C,D;
 int judge;	//勝利判定
 int count;	//ターンカウント

 scanf("%d %d %d %d",&A, &B, &C, &D);

 judge = 0;
 count = 2;
 while(judge == 0){

  if(count % 2 == 0)	//高橋の攻撃
  {
   C = C - B;
   if(C <= 0)
    judge = 1;
  }

  else			//青木の攻撃
  {
   A = A - D;
   if(A <= 0)
    judge = 2;
  }
  count += 1;
 }

 if(judge == 1)		//高橋の勝利
  printf("Yes\n");
 else if(judge == 2)	//青木の勝利
  printf("No\n");

 return 0;
}