def main():
    n,m = map(int,input().split())
    a = list(map(int,input().split()))
    a.sort()

    s = 0
    for i in range(m - 1):
        s += (a[i + 1] - a[i]) ** 2

    smin = s
    for i in range(n-m):
        s -= (a[i + 1] - a[i]) ** 2
        s += (a[i + m] - a[i + m - 1]) ** 2
        smin = min(smin,s)

    print(smin)

if __name__ == "__main__":
    main()