class Solution {
public:
    char toSmall(char ch) {
        if (ch <= 'Z' && ch >= 'A') return ch + ('a' - 'A');
        return ch;
    }

    string maskPII(string s) {
        int flag = -1, len = s.size();
        string ret;
        for (int i = 0; i < len; i++)
            if (s[i] == '@')
                flag = i;
        if (flag == -1) {
            string num;
            for (auto& i : s) {
                if (i <= '9' && i >= '0')
                    num += i;
            }
            ret += "***-***-";
            for (int i = num.size() - 4; i < num.size(); i++)
                ret += num[i];
            if (num.size() > 10) {
                int i = num.size() - 10;
                string t = "+";
                for (int j = 0; j < i; j++)
                    t += "*";
                t += "-";
                ret = t + ret;
            }
        }
        else {
            ret += toSmall(s[0]);
            ret += "*****";
            ret += toSmall(s[flag-1]);
            ret += "@";
            for (int i = flag + 1; i < len; i++) {
                ret += toSmall(s[i]);
            }
        }
        return ret;
    }
};