#include <bits/stdc++.h>

using namespace std;

const long long INF = 1LL << 60;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m; cin >> n >> m;
    assert(1 <= n && n <= 100000);
    assert(1 <= m && m <= 100000);
    assert(m <= n);
    vector<long long> a(n);
    for(int i = 0; i < n; i++){
        cin >> a[i];
        assert(1LL <= a[i] && a[i] <= 1000000000LL);
    }

    sort(a.begin(), a.end());
    vector<long long> s(n + 1);
    for(int i = 0; i < n; i++){
        long long diff = (a[i + 1] - a[i]);
        diff *= diff;
        s[i + 1] = s[i] + diff;
    }
    long long ans = INF;
    for(int i = 0; i < n - m + 1; i++){
        ans = min(ans, s[i + m - 1] - s[i]);
    }
    cout << ans << endl;
}