n = gets.to_i
a = gets.chomp.split.map(&:to_i)
ans = 0
ary = []

n.times do |i|
	ary[i] = a.count(i+1)
end

n.times do |i|
	if ary[i] > 1
		surplus = ary[i] - 1
		prei = i

		while surplus > 0
			i += 1 while ary[i] != 0
			ary[i] = 1
			ans += i - prei
			surplus -= 1
		end
		
		next
	end

	if ary[i] == 0
		ary[i] = 1
		prei = i
		i += 1 while ary[i] < 2
		ary[i] -= 1
		ans += i - prei

		next
	end
end

print ans