// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")


#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;(i)<(n);(i)++)
#define REP(i,a,n) for(ll i=(a);(i)<(n);(i)++)
#define rrep(i,n) for(ll i=(n)-1;(i)>=(0ll);(i)--)
#define RREP(i,a,n) for(ll i=(n)-1;(i)>=(a);(i)--)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define be(v) (v).begin(),(v).end()
#define all(v) (v).begin(),(v).end()
#define foa(i,v) for(auto& (i) : (v))
#define UQ(v) sort(be(v)), (v).erase(unique(be(v)), (v).end())
#define UQ2(v,cmp) sort(be(v)), (v).erase(unique(be(v),cmp), (v).end())
#define UQ3(v,cmp) sort(be(v),cmp), (v).erase(unique(be(v)), (v).end())
#define UQ4(v,cmp,cmp2) sort(be(v), cmp), (v).erase(unique(be(v),cmp2), (v).end())
#define LB(x,v) (lower_bound(be(v),(x))-(v).begin())
#define LB2(x,v,cmp) (lower_bound(be(v),(x),(cmp))-(v).begin())
#define UB(x,v) (upper_bound(be(v),(x))-(v).begin())
#define UB2(x,v,cmp) (upper_bound(be(v),(x),(cmp))-(v).begin())
#define dout()  cout << fixed << setprecision(20)
#define randinit() srand((unsigned)time(NULL))

template<class T, class U> bool chmin(T& t, const U& u) { if (t > u){ t = u; return 1;} return 0; }
template<class T, class U> bool chmax(T& t, const U& u) { if (t < u){ t = u; return 1;} return 0; }


ll Rnd(ll L=0, ll R=mod99){return rand()%(R-L)+L;}



void solve(){
    ll n,l,k;
    cin >> n >> l >> k;
    V<ll> v(n);
    rep(i,n) cin >> v[i];
    sort(be(v));
    ll L = -1, R = l;
    while(L+1!=R){
    	ll mid = (L+R)/2;
    	map<ll,ll> mp;
    	for(auto x:v){
    		if(x - mid < 0){
    			mp[0] ++;
    			mp[l] --;
    			mp[x - mid + l] ++;
    		}else{
    			mp[x-mid] ++;
    		}
    		if(x + mid > l){
    			mp[l] --;
    			mp[0] ++;
    			mp[x + mid - l] --;
    		}else{
    			mp[x+mid] --;
    		}
    	}
    	ll flag = 1;
    	ll s = 0;
    	for(auto [x,y]:mp){
    		s += y;
    		if(s < k and x != l) flag = 0;
    	}
    	if(flag) R = mid;
    	else L = mid;
    }
    cout << R << endl;
}





int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t=1;
    cin >> t;
    rep(i,t) solve();
}