Function GAMMP(A, X)
    If X < 0# Or A <= 0# Then
        Print "PAUSE"
        Exit Function
    End If
    If X < A + 1# Then
        Call GSER(GAMSER, A, X, GLN)
        GAMMP = GAMSER
    Else
        Call GCF(GAMMCF, A, X, GLN)
        GAMMP = 1# - GAMMCF
    End If
End Function