Roman Numerals to Integer

romanstointeger.cpp

#include<iostream>
#include<string>
using namespace std;

int getvalue(char r)
{
    if (r == 'I')
        return 1;
    if (r == 'V')
        return 5;
    if (r == 'X')
        return 10;
    if (r == 'L')
        return 50;
    if (r == 'C')
        return 100;
    if (r == 'D')
        return 500;
    if (r == 'M')
        return 1000;

    return -1;
}
int main()
{

    int sum=0;
    string str;
    string:: iterator it;
    cin>>str;
    for(it=str.begin();it!=str.end();it++)
    {
        int v1=getvalue(*it);
        int v2=getvalue(*(it+1));
        if(v1<v2)
        {
            sum=sum-v1;
            sum=sum+v2;
            it++;
        }
        else
            sum=sum+v1;
    }
    cout<<endl<<sum;
}