Link to the problem : Cf_739_E I am getting TLE in test case — 5 and have gone through the code many times, but cannot find any bug or optimisation. Any help is appreciated.

ll solve()
{
    string s;
    cin >> s;
    vector<ll> st(26, 0);
    string rm = "";
    string final = "";
    for (ll i = s.size() &mdash; 1; i >= 0; i--)
    {
        if (st[s[i] &mdash; 'a'] == 0)
        {
            st[s[i] &mdash; 'a'] = 1;
            rm = rm + s[i];
        }
        else
        {
            st[s[i] &mdash; 'a']++;
        }
    }
    reverse(rm.begin(), rm.end());
    ll total = 0;
    for (ll i = 0; i < rm.size(); i++)
    {
        if (st[rm[i] &mdash; 'a'] % (i + 1) != 0)
        {
            cout << -1 << endl;
            return 0;
        }
        st[rm[i] &mdash; 'a'] = st[rm[i] &mdash; 'a'] / (i + 1);
        total += st[rm[i] &mdash; 'a'];
    }
    vector<ll> st2(26, 0);
    for (ll i = 0; i < total; i++)
    {
        final = final + s[i];
        st2[s[i] &mdash; 'a']++;
    }
    ll start = total;
    string tmp = final;
    string sb = final;
    for (ll i = 0; i < rm.size(); i++)
    {
        string tmp2 = "";
        for (ll j = 0; j < tmp.size(); j++)
        {
            if (tmp[j] != rm[i])
            {
                tmp2 += tmp[j];
            }
        }
        tmp = tmp2;
        sb += tmp2;
    }
    if (sb != s)
    {
        cout << -1 << endl;
        return 0;
    }
    cout << final << " " << rm << endl;
    return 0;
}