n, k = map(int, input().split())
a = list(map(int, input().split()))
a.sort()

b = [0] * (n-1)

for i in range(n-1):
    b[i] = abs(a[i] - a[i+1])

b.sort()
ans = 0
for i in range(n-k):
    ans += b[i]

print(ans)