# -*- coding: utf-8 -*-
"""
No.615 集合に分けよう
https://yukicoder.me/problems/no/615

"""
import sys
from sys import stdin
input = stdin.readline


def solve(N, K, numbers):
    numbers.sort()
    gaps = []
    for i in range(1, N):
        gaps.append((-(numbers[i] - numbers[i-1]), i))
    gaps.sort()
    gaps = gaps[:K-1]

    ans = 0
    b = 0
    for gap, pos in gaps:
        ans += numbers[pos-1] - numbers[b]
        b = pos
    ans += numbers[-1] - numbers[b]
    return ans


def main(args):
    N, K = map(int, input().split())
    numbers = [int(x) for x in input().split()]
    ans = solve(N, K, numbers)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])