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

var v0 = c / b
if c % b != 0 { v0 += 1 }
var v1 = a / d
if a % d != 0 { v1 += 1 }

if v0 <= v1 {
  print("Yes")
} else {
  print("No")
}
