Module P1
Sub main()

    Dim RD As String
    Dim SD() As String
    
    Dim N As Long
    Dim A As String
    Dim B As String
    Dim C As String
    
    
'    RD = Console.Readline
'    SD = Split(RD, " ")
'    N = SD(0)
'    A = SD(1)
'    B = SD(2)
'    C = SD(3)
    
    N = Console.Readline
    A = Console.Readline
    B = Console.Readline
    C = Console.Readline
    
    
    Dim ChrIdx As Long
    Dim Cnt As Long
    
    For ChrIdx = 1 To CLng(N)
    
        If Mid(A, ChrIdx, 1) = Mid(B, ChrIdx, 1) And _
           Mid(A, ChrIdx, 1) = Mid(C, ChrIdx, 1) And _
           Mid(B, ChrIdx, 1) = Mid(C, ChrIdx, 1) Then
            Cnt = Cnt + 0
        ElseIf _
           Mid(A, ChrIdx, 1) = Mid(B, ChrIdx, 1) And _
           Mid(A, ChrIdx, 1) <> Mid(C, ChrIdx, 1) Then
            Cnt = Cnt + 1
        ElseIf _
           Mid(A, ChrIdx, 1) <> Mid(B, ChrIdx, 1) And _
           Mid(A, ChrIdx, 1) = Mid(C, ChrIdx, 1) Then
            Cnt = Cnt + 1
        ElseIf _
           Mid(A, ChrIdx, 1) <> Mid(B, ChrIdx, 1) And _
           Mid(A, ChrIdx, 1) <> Mid(C, ChrIdx, 1) And _
           Mid(B, ChrIdx, 1) = Mid(C, ChrIdx, 1) Then
            Cnt = Cnt + 1
        ElseIf _
           Mid(A, ChrIdx, 1) <> Mid(B, ChrIdx, 1) And _
           Mid(A, ChrIdx, 1) <> Mid(C, ChrIdx, 1) And _
           Mid(B, ChrIdx, 1) <> Mid(C, ChrIdx, 1) Then
            Cnt = Cnt + 2
        End If
        
    
           
    Next
    
    Console.Writeline (Cnt)

End Sub

end Module