Roman to Decimal converter

/*  Simple & correct program by Aakash Jain.
    Compare http://pastebin.com/9HxVCszK
*/

#include<iostream>
#include<ctype.h>
using namespace std;

int val (char c)
{
        int temp=0;
        switch (toupper(c))
        {
                case 'I': temp=1; break;
                case 'V': temp=5; break;
                case 'X': temp=10; break;
                case 'L': temp=50; break;
                case 'C': temp=100; break;
                case 'D': temp=500; break;
                case 'M': temp=1000; break;
                default : temp=0;
        }
        return temp;
}

int main()
{
        char roman[10]={0};
        int ans=0;
        int temp=0;
        cin>>roman;
        for (int i=0; roman[i] != '\0'; i++)
        {
                temp=val(roman[i]);
                if (temp==0)
                {
                        cout<<"Invalid input"<<endl;
                        return 1;
                }
                if (temp>=val(roman[i+1]))
                        ans+=temp;
                else
                        ans-=temp;
        }
        cout<<ans<<endl;
        return 0;
}