#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define MAX(a, b) ((a) > (b) ? (a) : (b))

int main(void)
{
long A, B, C, D, index;
  
  scanf("%ld %ld %ld %ld", &A, &B, &C, &D);
  for (index = 0; index < 100; ++index) {
    if (index % 2 == 0) {
      // 高橋君
      C -= B;
    } else {
      // 青木君
      A -= D;
    }
    if (A <= 0 || C <= 0) break;
  }
  if (A <= 0) {
    printf("No\n");
  } else {
    printf("Yes\n");
  }
    
  return 0;
}
