n, k = [int(x) for x in input().split()]
xs = [int(x) for x in input().split()]
xs.sort()
n = len(xs)
ds = []
s = 0
for i in range(n-1):
    ds.append(xs[i+1] - xs[i])
    s += ds[-1]
ds.sort()

print(s - sum(ds[n-k:]))