class Solution {
public:
    int romanToInt(string s) {

        int res =0;
        int temp  = 0;
        for(int i = 0; i<s.size(); i++)
        {
            char sym = s[i];
            int pos = 0;
            switch(sym)
            {
                case 'I': pos = 1; break;
                case 'V': pos = 5; break;
                case 'X': pos = 10; break;
                case 'L': pos = 50; break;
                case 'C': pos = 100; break;
                case 'D': pos = 500; break;
                case 'M': pos = 1000; break;
                default : return 0;
            }
            res += pos;
            if(temp<pos)
            {
                res -= 2*temp;
            }
            temp = pos;
        }

        return res;

    }
};