#include<stdio.h>
int main(void) {
  int A, B, C, D;
  int turn = 1; 
  
  scanf("%d %d %d %d", &A, &B, &C, &D);
  
  while(A > 0 && C > 0) {
    if(turn % 2 == 0) {
      A -= D;
    }else{
      C -= B;
    }
    turn++;
  }
  if(A > 0) {
    printf("Yes");
  }else{
    printf("No");
  }
  return 0;
}