#include <algorithm>
#include <cassert>
#include <iostream>
#include <vector>
using namespace std;
using ll = long long;

int main() {
    int n, m;
    cin >> n >> m;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) cin >> a[i];

    assert(1 <= m && m <= n);
    assert(1 <= n && n <= 100000);
    for (int i = 0; i < n; ++i) assert(1 <= a[i] && a[i] <= 1000000000);

    sort(a.begin(), a.end());
    ll ans = 0;
    for (int i = 0; i < m - 1; ++i) {
        ll d = a[i] - a[i + 1];
        ans += d * d;
    }

    ll s = ans;
    for (int l = 1; l < n - m; ++l) {
        int r = l + m - 1;
        ll ld = a[l - 1] - a[l];
        ll rd = a[r - 1] - a[r];
        s = s - (ld * ld) + (rd * rd);
        if (ans > s) {
            ans = s;
        }
    }

    cout << ans << endl;
    return 0;
}