#include<stdio.h>

int main(void){
  int a, b, c, d, flag = 0;

  scanf("%d%d%d%d", &a, &b, &c, &d);

  while(a > 0 && c > 0){
    if(flag == 0){
      c -= b;
      flag = 1;
    }else{
      a -= d;
      flag = 0;
    }
  }

  if(flag == 0){
    printf("No");
  }else{
    printf("Yes");
  }

  return 0;
}
