#coding: utf-8

def main():
  n,k = map(int, input().split(' '))
  an = list(map(int, input().split(' ')))
  an = sorted(an)
  diff_list = diff(an)
  for _ in range(k-1):
    diff_list.remove(max(diff_list))
  print(sum(diff_list))


def diff(an):
  diff_list = [an[i] - an[i-1] for i in range(1,len(an))]
  return diff_list


if __name__ == '__main__':
  main()