Hash

ll get_hash (string s) {
    ll p = 31, res = 0;
    for (int i = 0; i < s.length(); i++) {
        res += ((s[i] - 'a' + 1) * (p % mod)) % mod;
        res %= mod;
        p *= 31; p %= mod;
    }
    return res;
}