#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef unsigned long long ull;
const int N = 2000086, MOD = 1e9 + 7, INF = 0x3f3f3f3f;
ll res;
int n, m, cnt, w[N];

int k;

bool check(int mid) {
	priority_queue<int, vector<int>, greater<int> > q, q2;
	for (int i = 1; i < n + 1; i++)
		if (w[i] <= mid) q.push(w[i]);
		else if (m - w[i] <= mid) q.push(w[i] - m);
		else q2.push(w[i]);
	if (q.size() < k) return 0;
	
	while (q.size()) {
		auto u = q.top(); q.pop();
		q2.push(u + m);
		int ne = u + mid + 1;
		if (ne >= m) break;
		while (q.size() && q.top() == u) {
			q.pop();
			q2.push(u + m);
		}
		while (q2.size() && q2.top() - (ne - 1) <= mid) {
			if (ne - q2.top() <= mid) {
				q.push(q2.top());
				q2.pop();
			} else {
				q2.push(q2.top() + m);
				q2.pop();
			}
		}
		if (q.size() < k) return 0;
	}
	return 1;
}

void solve() {
	int l = 0, r = m;
	while (l < r) {
		int mid = l + r >> 1;
		if (check(mid)) r = mid;
		else l = mid + 1;
	}
	printf("%d\n", l);
}

int main() {
	int T;
	cin >> T;
	while (T--) {
		cin >> n >> m >> k;
		for (int i = 1; i < n + 1; i++) scanf("%d", w + i);
		solve();
	}
	return 0;
}