#include <iostream>
#include <vector>
#include <algorithm>
#include <climits>
using namespace std;

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

    sort(a.begin(), a.end());

    vector<long long> b(n - 1), s(n);
    for (int i = 0; i < n - 1; i++) {
        b[i] = static_cast<long long>(a[i + 1] - a[i]) * (a[i + 1] - a[i]);
    }
    for (int i = 1; i < n; i++) {
        s[i] = s[i - 1] + b[i - 1];
    }

    long long min_sum = LLONG_MAX;
    for (int i = 0; i <= n - m; i++) {
        min_sum = min(min_sum, s[i + m - 1] - s[i]);
    }

    cout << min_sum << endl;
    return 0;
}