#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
template <class T, class F>
T binarySearch(T ok, T ng, const F &f) {
	while (abs(ok - ng) > 1) {
		T mid = (ok + ng) / 2;
		(f(mid) ? ok : ng) = mid;
	}
	return ok;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int t; cin >> t;
	while (t--) {
		int n, m, k; cin >> n >> m >> k;
		vector<int>x(n);
		rep(i, n)cin >> x[i];
		auto f = [&](const long long tar)->bool {
			map<int, int>mp;
			mp[0] = 0;
			mp[m] = 0;
			rep(i, n) {
				int l = x[i] - tar;
				int r = x[i] + tar;
				if (l < 0) {
					mp[m + l]++;
					mp[m]--;
					l = 0;
				}
				mp[l]++;
				mp[min(m, r)]--;
				if (r > m) {
					mp[0]++;
					mp[r - m]--;
				}
			}
			int now = 0;
			for (auto[key, val] : mp) {
				if (key == m)continue;
				now += val;
				if (now < k)return false;
			}
			return true;
		};
		auto ans = binarySearch<int>(((m + 1) / 2), 0, f);
		cout << ans << endl;
	}
	return 0;
}