ll toDecimal(string s, ll n) {
    ll x = 0;
    for (ll i = 0; i < s.length(); i++) {
        x = x * n + s[i] - (s[i] >= 'A' ? 'A' - 10 : '0');
    }
    return x;
}

string fromDecimal(ll x, ll k) {
    string s;
    ll d;
    while (x) {
        d = x % k;
        s = char(d + (d >= 10 ? 'A' - 10 : '0')) + s;
        x /= k;
    }
    return s;
}