let abcd = readLine()!.split(separator: " ").map { Int($0)! }
let (a, b, c, d) = (abcd[0], abcd[1], abcd[2], abcd[3])

if (Double(c) / Double(b)).rounded(.up) <= (Double(a) / Double(d)).rounded(.up) {
  print("Yes")
} else {
  print("No")
}
