n, k = gets.split.map(&:to_i)
a = gets.split.map(&:to_i).sort
ans = a[-1] - a[0]
b = []
(n-1).times do |i|
    b.push(a[i + 1] - a[i])
end
b.sort!.reverse!
(k-1).times do |i|
    ans -= b[i]
end
p ans