N = gets.to_i
R = gets.split.map { _1.to_i - 1 }

first = [10**18] * N
R.each_with_index do |r, i|
    first[r] = [first[r], i].min
end
(0 ... N - 1).reverse_each do |i|
    first[i] = [first[i], first[i + 1]].min
end

ans = 0
right = N - 1
while right != 0
    right = first[right]
    ans += 1
end

puts ans