void init(int a, int b, int p, int m) {
    for (int i = 0; i < m; i++) {
        ll temp = quick_pow(a, i, p);
        mp[(temp * b) % p] = i;
    }
}
int BSGS(int a, int b, int p) {
    mp.clear(), b %= p;
    int m = (int)sqrt(p) + 1;  //害怕精度不够
    init(a, b, p, m);
    a = quick_pow(a, m, p);
    if (a == 0) return b ? -1 : 1;
    for (int i = 0; i <= m; i++)
    {
        int temp = quick_pow(a, i, p);
        int j;
        if (mp.count(temp)) {
            j = mp[temp];
        }
        else j = -1;
        if (j >= 0 && i * m - j >= 0)  return i * m - j;
    }
    return -1;
}