#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto& i:a)
#define ff first 
#define ss second 
#define all(a) begin(a),end(a)
#define allr(a) rbegin(a),rend(a)
#define pb push_back
using ll =long long;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
using vi=vector<int>;
using vll=vector<ll>;
template<class T> inline bool chmin(T& a,T b){return a>b?a=b,1:0;}
template<class T> inline bool chmax(T& a,T b){return a<b?a=b,1:0;}
const int INFI=numeric_limits<int>::max()/2;
const ll INFL=numeric_limits<ll>::max()/2;
ll n,l,k;
vll x;
void solve(){
    sort(all(x));
    auto f=[&](ll p)->bool {
        if(2*p>=l)return true;
        vector<ll> v;
        v.pb(0);v.pb(l-1);v.pb(l);
        rep(i,0,n){
            ll L=(l+x[i]-p)%l;
            ll R=(L+2*p)%l;
            v.pb(L);v.pb(R);
        }
        sort(all(v));v.erase(unique(all(v)),end(v));
        ll sz=v.size();
        vll imos(sz);
        rep(i,0,n){
            ll L=(l+x[i]-p)%l;
            ll R=(L+2*p)%l;
            ll Li=distance(begin(v),lower_bound(all(v),L));
            ll Ri=distance(begin(v),lower_bound(all(v),R));
            if(Li<Ri){
                imos[Li]++;imos[Ri]--;
            }else{
                imos[0]++;imos[Ri]--;
                imos[Li]++;
            }
        }
        
        rep(i,0,sz-1){
            if(i!=0){
                imos[i]+=imos[i-1];
            }
            if(imos[i]<k)return false;
        }
        return true;
        
    };
    ll ok=l,ng=0;
    while(abs(ok-ng)>1){
        ll mid=(ok+ng)/2;
        if(f(mid))ok=mid;
        else ng=mid;
    }
    cout<<ok<<'\n';
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t;cin>>t;
    while(t--){
        cin>>n>>l>>k;
        x.resize(n);
        rep(i,0,n)cin>>x[i];
        solve();
    }
    return 0;
}
/*
*/