N,K = map(int,input().split())
a = list(map(int,input().split()))
a.sort()
import sys
if N == K:
    print(0)
    exit()

b = []
for i in range(N-1):
    b.append(a[i+1] - a[i])
b.sort()
ans = sum(b)
for _ in range(K-1):
    ans -= b.pop()
print(ans)