
Imports System.Console
Module Module1
    Dim ans As Int64
    Dim max As Int64
    Dim n, k, x, t As Int64
    Sub Main()
        Dim s() As String = ReadLine().Split
        n = s(0)
        x = s(1)
        t = s(2)
        ans = n \ x
        If n Mod x <> 0 Then
            ans += 1
        End If
        ans *= t
        WriteLine(ans)
    End Sub
End Module
