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

class Solution {
private: 
    unordered_map<char, int> symbolValues = {
    {'I', 1},
    {'V', 5},
    {'X', 10},
    {'L', 50},
    {'C', 100},
    {'D', 500},
    {'M', 1000},
    };

public:
    int romanToInt(string s)
    {
        int ans = 0;
        int n = s.length();
        for (int i = 0; i < n; i++){
            int value = symbolValues[s[i]];
            if (i < n - 1 && value < symbolValues[s[i+1]]){
                ans -= value;
            } else {
                ans += value;
            }
        }
        return ans;
    }

};