#include <bits/stdc++.h>

using std::cin;
using std::cout;
using std::ios;

const int N = 2e5 + 5;
int n, p, ans, b[N], a[N];
int T_data;

template <class T>
inline void CkMax(T &x, T y) {x < y ? x = y : 0;}

inline int quick_pow(int x, int k)
{
    int res = 1;
    while (k)
    {
        if (k & 1)
            res = 1ll * res * x % p;
        x = 1ll * x * x % p;
        k >>= 1;
    }
    return res;
}

inline int check(int x, int q)
{
    int cnt = 0;
    for (int i = x + 1; i <= n; ++i)
    {
        if (1ll * a[x] * q % p == a[i])
            x = i, ++cnt;
    }
    return cnt;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    srand(time(0));
    cin >> T_data;
    while (T_data--)
    {
        cin >> n >> p;
        for (int i = 1; i <= n; ++i)
            cin >> a[i], b[i] = quick_pow(a[i], p - 2);
        ans = 0;
        for (int t = 1; t <= 200; ++t)
        {
            int k = 1ll * rand() * rand() % (n - 2) + 1;
            CkMax(ans, 2 + check(k + 1, 1ll * a[k + 1] * b[k] % p));
            CkMax(ans, 2 + check(k + 2, 1ll * a[k + 2] * b[k] % p));
            CkMax(ans, 2 + check(k + 2, 1ll * a[k + 2] * b[k + 1] % p));
        }
        if (ans >= (n + 1 >> 1))
            cout << ans << '\n';
        else 
            cout << "-1\n";
    }
}