#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <bitset>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <cassert>

const int N = 2e5 + 7;
using namespace std;
int n,m, a[N],b[N], x;
set<int> s;

bool check(long long val) {
    long long cnt_add = 0;
    for (int i = 1; i <= n; i++) {
        a[i] = 0;
    }
    for (int i = 0; i < m; i++) {
        if (a[b[i]] + 1 <= val) {
            a[b[i]]++;
        }
        else {
            cnt_add++;
        }
    }
    for (int i = 1; i <= n; i++) {
        cnt_add -= (val - a[i]) / 2;
    }
    return cnt_add <= 0;
}

void solve() {
    cin >> n >> m;
    for (int i = 0; i < m; i++) {
        cin >> b[i];
    }

    long long L = 0, R =n * 2 + 1;
    while (R - L > 1) {
        long long mid = (L + R) / 2;
        if (check(mid)) {
            R = mid;
        }
        else {
            L = mid;
        }
    }
    cout << R << "\n";
}

int main()
{
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
#else
    std::ios::sync_with_stdio(false);
    cin.tie(0);
#endif
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
}