n,k=map(int,input().split())
a=list(map(int,input().split()))
a.sort()

sumn=[0]*n
sumnn=[0]*n
for i in range(1,n):
  if 0<i<n-1:
    sumnn[i]=a[i+1]-a[i]+(a[i]-a[i-1])
    sumn[i]=a[i]-a[i-1]
  else:
    sumnn[i]=a[i]-a[i-1]
    sumn[i]=a[i]-a[i-1]
k-=1
sumn.sort()
while k:
  sumn.pop()
  k-=1
print(sum(sumn))