#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

const ll mod = 1e9 + 7;
const ll mod2 = 998244353;

ll gcd(ll a, ll b) {
    return b ? gcd(b, a % b) : a;
}

ll pow(ll a, ll b) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans *= a;
        b >>= 1;
        a *= a;
    }
    return ans;
}

ll pow(ll a, ll b, ll c) {
    ll ans = 1;
    while (b) {
        if (b & 1) ans = (ans * a) % c;
        b >>= 1;
        a = (a * a) % c;
    }
    return ans;
}

void check(bool b) {
    if (b)
        cout << "Yes\n";
    else
        cout << "No\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int t = 1;
    cin >> t;
    while (t--) {
        ll n;cin>>n;
        ll p;cin>>p;
        ll k;cin>>k;
        vector<ll>a(n);
        for (int i = 0; i < n; ++i) {
            cin>>a[i];
        }
        ll l=1, r=p/2+p%2;
        while (l<r){
            ll mid=(l+r)/2;
            deque<pair<ll,ll>>v;
            for (int i = 0; i < n; ++i) {
                ll l1=a[i];
                ll r1=a[i]+mid-1;
                v.push_back({l1,1});
                if (r1<p-1){
                    v.push_back({r1+1,-1});
                } else {
                    v.push_back({0,1});
                    v.push_back({r1-p+1,-1});
                }
            }
            for (int i = 0; i < n; ++i) {
                if (a[i]==0){
                    v.push_back({p-mid,1});
                    continue;
                }
                v.push_back({a[i],-1});
                ll l1=a[i]-mid;
                if (l1<0){
                    v.push_back({0,1});
                    v.push_back({p+l1,1});
                } else {
                    v.push_back({l1,1});
                }
            }
            sort(v.begin(),v.end());
            bool ok=true;
            ll cnt=0;
            while (!v.empty()){
                auto x=v.front().first;
                while (!v.empty() && v.front().first==x){
                    cnt+=v.front().second;
                    v.pop_front();
                }
                if (cnt<k){
                    ok=false;
                    break;
                }
            }
            if (ok){
                r=mid;
            } else {
                l=mid+1;
            }
        }
        cout<<l<<'\n';
    }
    return 0;
}