from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math

N,K = map(int,input().split())
A = list(map(int,input().split()))
A.sort()
if N==1:
    print(0)
    exit()
B = [A[i+1]-A[i] for i in range(N-1)]
B.sort(reverse=True)
S = A[-1]-A[0]
print(S - sum(B[:K-1]))