def main():
    N, K = map(int, input().split())
    if N == K:
        print(0)
        exit()
    A = tuple(map(int, input().split()))
    if K == 1:
        print(max(A) - min(A))
        exit()

    a = sorted(A)
    slice_ = [0] * (N - 1)
    for i in range(1, N):
        slice_[i-1] = (a[i] - a[i-1], i)
    slice_.sort(reverse=True)

    splt = sorted(slice_[:K-1], key=lambda x: x[1])
    s = 0
    total = 0
    for _, e in splt:
        total += max(a[s:e]) - min(a[s:e])
        s = e
    total += max(a[s:]) - min(a[s:])
    print(total)

main()