#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> PII;
const int N = 2e5 + 10;

ll n, p, b[N];
ll ksm(ll a, ll b) {
	ll res = 1;
	while (b) {
		if (b & 1) res = res * a % p;
		a = a * a % p;
		b >>= 1;
	}
	return res;
}
unordered_map<ll, ll> mp;
void solve() {
	scanf("%lld%lld", &n, &p);
	for (int i = 1; i <= n; i++) scanf("%lld", &b[i]);
	for (int i = 1; i < n; i++) {
		ll q = b[i + 1] * ksm(b[i], p - 2) % p;
		mp[q]++;
		if (i < n - 1) q = b[i + 2] * ksm(b[i], p - 2) % p, mp[q]++;
	}
	vector<ll> v;
	for (auto it = mp.begin(); it != mp.end(); it++) {
		if (it->second >= n / 4) v.push_back(it->first);
	}
	ll ans = -1;
	for (int i = 0; i < v.size(); i++) {
		ll q = v[i], inv = ksm(q, p - 2);
		unordered_map<ll, ll> mmp;
		ll tmp = 0;
		for (int j = 1; j <= n; j++) {
			ll t = mmp[b[j]];
			t = max(t, mmp[b[j] * inv % p] + 1);
			mmp[b[j]] = t;
			tmp = max(tmp, t);
		}
		if (tmp >= (n + 1) / 2) ans = max(ans, tmp);
	}
	printf("%lld\n", ans);
}
int main() {
	int _ = 1;
	cin >> _;
	while (_--) solve();
	return 0;
}