# coding: utf-8
# Your code here!

n,k = map(int,input().split())
lst = list(map(int,input().split()))
lst.sort()
indx_lst = []

if n==k:
    print(0)
else:
    for i in range(n-1):
        x = lst[i+1] - lst[i]
        indx_lst.append([x,i])
        
    indx_lst.sort()
    ans_lst = []
    
    for i in range(1,k):
        ans_lst.append(indx_lst[-i][1])
    
    ans_lst.sort()
    ans_lst.append(n-1)
    
    indx = 0
    total = 0
    
    for i in range(k):
        total += lst[ans_lst[i]] - lst[indx]
        indx = ans_lst[i] + 1
    print(total)