Sub Find_Matches()
    Dim CompareRange As Variant, x As Variant, y As Variant

    Set CompareRange = Range("D1:D5")

    For Each x In Selection
        For Each y In CompareRange
            If x = y Then x.Offset(0, 1) = x
            If x = y Then x.Offset(0, 2) = y.Offset(0, 1)
        Next y
    Next x
End Sub

import numpy as np
a=np.loadtxt("a.csv",delimiter=',')
x,y = a[:,0],a[:,1]
v=np.select([x==y],[x],default = -1)
np.savetxt("b.csv",np.c_[x,y,v],delimiter=',')