# from collections import

def readints():
  return list(map(int, input().split()))

def main():
  N, M = readints()
  A = readints()
  A = sorted(A)
  ans = cur = sum((A[i+1] - A[i])**2 for i in range(M - 1))
  for i in range(M - 1, N - 1):
    cur += (A[i+1] - A[i])**2 - (A[i+2-M] - A[i+1-M])**2
    ans = min(ans, cur)
  print(ans)


if __name__ == '__main__':
  # import sys
  # sys.setrecursionlimit(550000)
  # flush = lambda: sys.stdout.flush()
  main()