from itertools import accumulate


def main():
    n, m = map(int, input().split())
    *a, = map(int, input().split())
    a.sort()
    a = [0] + [(a[i] - a[i-1])**2 for i in range(1, n)]
    a = list(accumulate(a))
    print(min(a[i+m-1] - a[i] for i in range(n-m+1)))


if __name__ == '__main__':
    main()