from operator import itemgetter

N, K = map(int, input().split())
A = list(map(int, input().split()))

ans = 0
A.sort()
d = [A[i + 1] - A[i] for i in range(N - 1)]
d = list(zip(d, range(N - 1)))
d.sort(reverse=True, key=itemgetter(0))
s = 0
for i in range(K):
    e = -1 if i == K - 1 else d[i][1]
    ans += A[e] - A[s]
    s = e + 1
print(ans)