#include <stdio.h>

int main (void){
  int a,b;
  int c,d;
  int i=0;
  scanf("%d %d %d %d",&a,&b,&c,&d);

  while( a > 0 || c > 0){
    if ( a <= 0){
      printf("No\n");
      break;
    }else  if ( c <= 0){
      printf("Yes\n");
      break;
    }
    if( i % 2 == 0) c -=b;
    else a -=d;  
    i++;
  }

  

  return 0;
  
}
