#include <bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T> istream& operator >> (istream& is, vector<T>& vec) {
    for(T& x : vec) is >> x;
    return is;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    vector<ll> a(n), s(n);
    cin >> a;
    sort(a.begin(), a.end());
    ll ans = 1ll << 61;
    for(int i = 0; i + 1 < n; i++){
        s[i + 1] = s[i] + (a[i + 1] - a[i]) * (a[i + 1] - a[i]);
    }
    for(int i = 0; i + m < n; i++){
        ans = min(ans, s[i + m - 1] - s[i]);
    }
    cout << ans << '\n';
}