Как сложить 100 пятидесятизначных чисел - VB

Sub Summa()
    Dim s1 As String
    Dim s2 As String
    Dim x As Integer
    Dim y As Integer
    Dim i As Integer
    Dim c As Integer
    Dim f As Integer
    
    Open "C:\Users\Юлия\Desktop\Программирование\числа.txt" For Input As #1
    c = 0
    
    Line Input #1, s1
    
    Do
        Line Input #1, s2
        s1 = Trim(StrReverse(s1))
        s2 = Trim(StrReverse(s2))
        For i = 1 To 50
            x = Val(Mid(s2, i, 1))
            y = Val(Mid(s1, i, 1))
            f = x + y + c
                        
            If f > 9 Then
                c = 1
                f = f - 10
            Else
                c = 0
            End If
            s1 = Mid(s1, 1, i - 1) & Str(f) & Mid(s1, i + 1, Len(s1) - i)
        Next i
    Loop Until EOF(1)
    
    Close #1
    s1 = StrReverse(s1)
    s1 = Mid(s1, 1, 20)
    Cells(1, 1) = s1
    
End Sub