n = gets.to_i
num = gets.strip.split.map(&:to_i)
ary = Array.new(n,0)
ary[0] = num[0]
ary[n-1] = num[n-2]
i = 1
if n != 2
  while i < n-1 do
    if num[i-1] >= num[i]
      ary[i] = num[i]
    else
      ary[i] = num[i-1]
    end
    i += 1
  end
end
puts ary.sum