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

#define rep(i, n) for( ll i = 0; i < n; i++ )
using ll = long long;

int main() {
	int N, M;
	cin >> N >> M;
	vector<ll> a( N );
	rep(i, N) cin >> a[i];
	sort(a.begin(), a.end());
	ll ans = 0, b;
	rep(i, M - 1) {
		ll d = a[i + 1] - a[i];
		ans += d * d;
	}
	b = ans;
	for( int i = M - 1; i + 1 < N; i++ ) {
		int j = i - M + 1;
		ll d = a[j + 1] - a[j];
		b -= d * d;
		d = a[i + 1] - a[i];
		b += d * d;
		ans = min(ans, b);
	}
	cout << ans << endl;
}