#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; ++i)
#define all(a) (a).begin(), (a).end()

const ll mod = 1e9 + 7;

int main() {
    cin.tie(nullptr);
    
    int N, M;
    cin >> N >> M;
    vector<ll> A(N);
    rep(i, 0, N) cin >> A[i];

    if (N == 1) {
        cout << 0 << '\n';
        return 0;
    }
    
    sort(all(A));
    
    vector<ll> S(N - 1);
    rep(i, 0, N - 1) S[i] = (A[i + 1] - A[i])*(A[i + 1] - A[i]);
    rep(i, 1, N - 1) S[i] += S[i - 1];
    
    ll ans = LLONG_MAX;
    rep(i, 0, N - M + 1) {
        if (i == 0) ans = min(ans, S[i + M - 1]);
        else ans = min(ans, S[i + M - 2] - S[i - 1]);
    }
    
    cout << ans << '\n';
}