Imports System
Imports System.IO

Module Module1

    Sub Main(ByVal args As String())

        Dim s As String() = Console.ReadLine().Split(" ")
        Dim ans As String

        Dim ta As Decimal = Math.Ceiling(CLng(s(2)) / CLng(s(1)))
        Dim ao As Decimal = Math.Ceiling(CLng(s(0)) / CLng(s(3)))

        If ta <= ao Then
            ans = "Yes"
        Else
            ans = "No"
        End If

        Console.Write(ans)

    End Sub

End Module