from heapq import *

N, K = map(int, input().split())
A = list(map(int, input().split()))
A.sort()
ans = A[-1] - A[0]
H = []
for i in range(N - 1):
    heappush(H, -A[i + 1] + A[i])

for i in range(K - 1):
    ans += heappop(H)
print(ans)