
Imports System.Console
Module Module1
    Dim n As Int64
    Dim ans As Int64
    Sub Main()
        n = ReadLine()
        Dim a As Integer = 1
        Dim w As Int64
        Do Until w + 26 ^ a >= n
            w += 26 ^ a
            a += 1
        Loop
        If a >= 2 Then
            For i = a To 2 Step -1
                n -= 26 ^ (i - 1)
            Next
        End If
        Dim ans As String = ""
        For i = a To 1 Step -1
            Dim d As Double = n / 26 ^ (i - 1)
            Dim s As Integer
            s = Math.Ceiling(d)
            ans &= ToCher(s)
            n -= (s - 1) * (26 ^ (i - 1))
        Next
        WriteLine(ans)
    End Sub
    Function ToCher(ByVal k As Integer) As Char
        Return Chr(96 + k)
    End Function
End Module
