N = gets.to_i
P = gets.split(" ").map{|s| s.to_i}

idx = {}

P.each_with_index {|x, i|
	idx[x] = i
}

cnt = 0
0.upto(N-2) {|i|
	while P[i] != i + 1 do
		j = idx[P[i]-1]
		idx[P[i]], idx[P[j]] = j, i 
		P[i], P[j] = P[j], P[i]
		cnt += 1
	end
}

puts cnt