def getlist():
	return list(map(int, input().split()))

N, K = getlist()
a = getlist()
a = sorted(a)
b = []
for i in range(N - 1):
	b.append(a[i + 1] - a[i])

b = sorted(b)
ans = 0
for i in range(N - K):
	ans += b[i]

print(ans)