static int palindromHalfLength(int i, String s) {
        int step = 1;
        char palChar = s.charAt(i-1);
        while (i-step>=0 && i+step<s.length()
                && s.charAt(i-step) == palChar
                && s.charAt(i+step) == palChar) step++;

        return step-1;
    }
    // Complete the substrCount function below.
    static long substrCount(int n, String s) {
        if (s.length() == 0) return 0;
        long res = 1;
        int countSimChar = 1;
        for (int i = 1; i < s.length(); i++) {
            if (s.charAt(i-1) == s.charAt(i)) {
                countSimChar++;
            }  else {
                res += palindromHalfLength(i, s);
                countSimChar = 1;
            }
            res += countSimChar;
        }
        return res;
    }