#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define inf 0x3f3f3f3f3f3f3f3f

const int maxn = 1e5 + 10;
const int mod = 1e9 + 7;
int n, m, k;
void solve()
{
    cin >> n >> m >> k;
    map<int, int> mp;
    vector<int> a(n * m + 1);
    for (int i = 1; i <= n * m; i++)
    {
        int x;
        cin >> a[i];
        // mp[(x + m - 1) / m]++;
    }
    if (k >= m)
    {
        cout << m << endl;
        return;
    }
    for (int i = 1; i <= n * m; i++)
    {
        mp[(a[i] + m - 1) / m]++;
        if (m - mp[(a[i] + m - 1) / m] >= m - mp[(a[i] + m - 1) / m] && k >= m - mp[(a[i] + m - 1) / m])
        {
            cout << i << endl;
            return;
        }
    }
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    cin >> t;
    while (t--)
        solve();
    return 0;
}