def diff(numbers):
    diffs = []
    for i in range(1,len(numbers)):
        diffs.append(numbers[i]-numbers[i-1])
    diffs.sort()
    return diffs

def main():
    N, K = list(map(int, input().split()))
    numbers = list(map(int, input().split()))
    if not len(numbers) == N:
        exit()

    numbers.sort()
    diffs = diff(numbers)
    ans = sum(diffs[:N-K])
    print(ans)

if __name__ == '__main__':
    main()