import sys

sys.setrecursionlimit(10 ** 6)
stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline().strip()
ntp = lambda: tuple(map(int, stdin.readline().split()))
mod = 10 * 9 + 7
inf = 2 << 60

n, k = na()
A = sorted(na())
B = sorted([A[i] - A[i - 1] for i in range(1, n)])

print(sum(B[:n - k]))