Правильный ответ 4.
Приведем все слагаемые к степени двойки. 2^4096+2^11-2^8.
2^4096 в двоичном представлении будет выглядеть как 1 и 4096 нулей. Прибавление к нему 2^11 добавит единицу в 12 разряд, если считать слева направо. Вычитание 2^8 даст 3 единицы, проэкспериментируйте 100000000000-100000000 = 11100000000. Итого 4 единицы.
На Visual Basic
Sub Roma
Dim R As String, N As Long, k As Integer, i As Integer
R = InputBox ("Vvedite Rimskoe chislo")
N = 0 : k = 0
i = 1
Do
k = InStr$(R, i, "M")
If k > 0 Then N = N + 1000
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "CM")
If k > 0 Then N = N - 100
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "D")
If k > 0 Then N = N + 500
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "CD")
If k > 0 Then N = N - 100
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "C")
If k > 0 Then
If (Mid$(R, k+1, 1) <> "D") And (Mid$(R, k+1, 1) <> "M") Then
N = N + 100
End If
End If
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "XC")
If k > 0 Then N = N - 10
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "L")
If k > 0 Then N = N + 50
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "XL")
If k > 0 Then N = N - 10
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "X")
If k > 0 Then
If (Mid$(R, k+1, 1) <> "C") And (Mid$(R, k+1, 1) <> "L") Then
N = N + 10
End If
End If
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "IX")
If k > 0 Then N = N - 1
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "V")
If k > 0 Then N = N + 5
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "IV")
If k > 0 Then N = N - 1
Loop While ((k > 0) And (i <= Len(R)))
i = 1
Do
k = InStr$(R, i, "I")
If k > 0 Then
If (Mid$(R, k+1, 1) <> "X") And (Mid$(R, k+1, 1) <> "V") Then
N = N + 1
End If
End If
Loop While ((k > 0) And (i <= Len(R)))
MsgBox (N)
End Sub