N,K=map(int,input().split())
a=list(map(int,input().split()))
a.sort()
b=[]
for i in range(N-1):
    b.append((a[i+1]-a[i],i))
b.sort(reverse=True)
c=[b[i][1] for i in range(K-1)]
c=set(c)
ans=0
check=set()
for i in range(N):
    check.add(a[i])
    if i in c or i==N-1:
        ans+=max(check)-min(check)
        check=set()
print(ans)