#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <numeric>
#include <array>
#include <tuple>
#include <cassert>
#include <random>
#include <chrono>
#define int long long

using namespace std;
using u32 = unsigned;
using i64 = long long;
using u64 = unsigned long long;
using PII = std::pair<int, int>;

//std::mt19937_64 rng {std::chrono::steady_clock::now().time_since_epoch().count()};
constexpr int N = 2e5 + 10;

void solve() {
    int n, m, k;
    std::cin >> n >> m >> k;
    std::vector<int> a(n * m + 1);

    for (int i = 1; i <= n * m; i ++) {
        std::cin >> a[i];
    }
    if (k >= m) {
        std::cout << m << "\n";
        return;
    }
    std::vector<int> cnt(n * m + 1);
    int maxx = 0;
    for (int i = 1; i <= n * m; i ++) {
        cnt[a[i] / m + 1] ++;
        maxx = std::max(maxx, cnt[a[i] / m + 1]);
        if (i >= m && maxx + k >= m) {
            std::cout << i << "\n";
            return;
        } 
    }
    return;
}
signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    int T = 1;
    std::cin >> T;
    while (T --) {
        solve();
    }
    return 0;
}