' FB 1.05.0 Win64

' The biggest integer which FB supports natively is 8 bytes so unable
' to calculate 1 millionth Hamming number without using an external
' "bigint" library such as GMP

Function min(x As Integer, y As Integer) As Integer
  Return IIf(x < y, x, y)
End Function

Function hamming(n As Integer) As Integer
  Dim h(1 To n) As Integer
  h(1) = 1
  Dim As Integer i = 1, j = 1, k = 1
  Dim As Integer x2 = 2, x3 = 3, x5 = 5

  For m As Integer = 2 To n
    h(m) = min(x2, min(x3, x5))
    If h(m) = x2 Then
      i += 1
      x2 = 2 * h(i)
    End If
    If h(m) = x3 Then
      j += 1
      x3 = 3 * h(j)
    End if
    If h(m) = x5 Then
      k += 1
      x5 = 5 * h(k)
    End If
  Next

  Return h(n)
End Function

Print "The first 20 Hamming numbers are :"
For i As Integer = 1 To 20
  Print hamming(i); " ";
Next
Print : Print
Print "The 1691st hamming number is :"
Print hamming(1691)
Print
Print "Press any key to quit"
Sleep