CHFCH Editorialist

#include <bits/stdc++.h>

using namespace std;

const int MX = (1<<20);


long long sum[MX];

long long get(int l , int r){

    if(r < 0 || l > r) return 0;

    long long ret = sum[r];

    if(l > 0) ret -= sum[l-1];

    return ret;


}

long long process(vector < int > v , int K){

    long long ret = (1ll << 60);

    if(K > v.size()) return ret;

    sum[0] = v[0];

    sum[v.size()] = 0;

    for(int j = 1 ; j < v.size() ; j++)
        sum[j] = v[j] + sum[j-1];

    for(int j = 0 ; j + K <= v.size() ; j++){

        long long l = j , r = j - 1 + K , mid = (l + r)/2;

        long long leftcost = (mid - l) * v[mid] - ((mid - l) * (mid - l + 1))/2 - get(l , mid - 1);

        long long rightcost = get(mid + 1 , r) - (r - mid) * v[mid] - ( (r - mid) * (r - mid + 1) / 2);

        ret = min(ret , leftcost + rightcost);


    }

    return ret;


}

vector < int > v[MX];

int n , arr[MX] , K , T;

int main(){

    scanf("%d",&T);

    while(T--){

        scanf("%d %d",&n,&K);

        set < int > S;


        for(int j = 1 ; j <= n ; j++){
            scanf("%d",&arr[j]);
            S.insert(arr[j]);
            v[arr[j]].clear();
        }

        for(int j = 1 ; j <= n ; j++){
            v[arr[j]].push_back(j);
        }

        long long ans = (1ll << 60);

        for(auto x : S)
            ans = min(ans , process(v[x] , K));

        if(ans == (1ll << 60)) ans = -1;

        cout<<ans<<endl;


    }

}