class Solution {
public:
    int n = 0;
    double temp;
    double g[30][30];
    bool vis[30];
    unordered_map<string, int> hash;
    int getID(string a) {
        if (!hash.count(a)) hash[a] = n ++;
        return hash[a];
    }
    vector<double> calcEquation(vector<vector<string>>& equations, vector<double>& values, vector<vector<string>>& queries) {
        for (int i = 0; i < equations.size(); i ++ ) {
            int a = getID(equations[i][0]), b = getID(equations[i][1]);
            g[a][b] = values[i], g[b][a] = 1 / values[i];
        }
        vector<double> res;
        for (auto& t : queries) {
            string a = t[0], b = t[1];
            if (!hash.count(a) || !hash.count(b)) res.push_back(-1);
            else {
                memset(vis, 0, sizeof vis);
                if (dfs(getID(a), getID(b), 1)) res.push_back(temp);
                else res.push_back(-1);
            }
        }
        return res;
    }
    bool dfs(int u, int b, double m) {
        if (u == b) {
            temp = m;
            return true;
        }
        vis[u] = true;
        for (int i = 0; i < n; i ++ ) {
            if (g[u][i] != 0 && !vis[i])
                if (dfs(i, b, m * g[u][i]))
                    return true;
        }
        return false;
    }
};