#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]);
    
    ll sum = 0;
    rep(i, 0, M - 1) sum += S[i];
    
    ll ans = sum;
    rep(i, 1, N - M + 1) {
        sum -= S[i - 1];
        sum += S[i + M - 1];
        ans = min(ans, sum);
    }
    
    cout << ans << '\n';
}