Roman Numeral Assignment

//roman numeral code
#include <iostream>
#include <string>
using namespace std;

class roman
{
public:
    string roman;

    void get() //gets user input
    {
        cout << "Please Input a Roman Numeral: ";
        cin >> roman;
        cout << "\n";
    }

    void check() //checks to see if number is valid
    {
        bool check = true;
        do
        {
            check = true;

            for (int i = 0; i < roman.size(); i++)
            {
                roman[i] = toupper(roman[i]);
                if (roman[i] != 'M' && roman[i] != 'D' && roman[i] != 'L' && roman[i] != 'C' && roman[i] != 'X' && roman[i] != 'V' && roman[i] != 'I')
                {
                    check = false;
                }
            }

            if (check == false) //retries if number is invalid
            {
                cout << "Invalid Input, Please Try Again: ";
                cout << "\n\nPlease Input a Roman Numeral: ";
                cin >> roman;
            }
        } while (check == false);
    }

    void convert()
    {

        int number = 0;
        int LastNumber = 0;
        int CurrentNumber = 0;
        for (int i = 0; i < roman.size() + 1; i++)
        {
            roman[i] = toupper(roman[i]); //assigns letters to a number

            if (roman[i] == 'M')
            {
                CurrentNumber = 1000;
            }
            else if (roman[i] == 'D')
            {
                CurrentNumber = 500;
            }
            else if (roman[i] == 'C')
            {
                CurrentNumber = 100;
            }
            else if (roman[i] == 'L')
            {
                CurrentNumber = 50;
            }
            else if (roman[i] == 'X')
            {
                CurrentNumber = 10;
            }
            else if (roman[i] == 'V')
            {
                CurrentNumber = 5;
            }
            else
            {
                CurrentNumber = 1;
            }
            if (CurrentNumber > LastNumber)
            {
                LastNumber = 0 - LastNumber;
            }
            number = number + CurrentNumber;
            LastNumber = CurrentNumber;
        }
        cout << number;
    }
};

int main() //main function
{
    roman romnum;
    romnum.get();
    romnum.check();
    romnum.convert();
    return -0;
}