#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ps(b) cout << (b ? "YES" : "NO") << '\n'
#define pc cout << "Case " << tc << ": "
#ifdef LOCAL
#include "def.h"
#else
#define ck(...) 
#endif
const ll M = 1e9 + 7, N = 2e5 + 5;

void test(int tc) {
    ll a = 0, b = 0, c = 0, d = 0, i = 0, j = 0, k = 0, m = 0, n = 0, q = 0;
    cin >> n >> k;
    map<ll, ll> mp;
    for (i = 0; i < n; ++i) { cin >> a;
        mp[a]++;
    }
    multimap<int, int, greater<>> mmp;  // descending order
    for(auto &[f, s]:mp) mmp.emplace(s, f);
    a = 0;
    while(n){
        if(a==0) a = k;
        for(auto [f,s]:mmp){
            if(mp[s]==0) {
                c++;
            }
            else{
                mp[s]--;
            }
            --n;
            if(--a == 0 or !n)
                break;
        }
    }
    cout << c;
    cout << '\n';
}

signed main() {
    cin.tie(0)->sync_with_stdio(0); cin.exceptions(cin.failbit|cin.badbit);
    int tc = 0, t = 1;
    cin >> t;
    while (tc < t) test(++tc);
    return 0;
}