def min(a, b)
   (a < b) ? a : b
end

n = gets.chomp.to_i

tmp = gets.chomp
b_nums = tmp.split(" ")
b_nums.map! do |b|
  b.to_i
end
#b_nums << b_nums[-1]

result = b_nums[0] + b_nums[-1]

idx = 1
while idx < n-1 do
  result += min(b_nums[idx-1], b_nums[idx])
  idx += 1
end

puts result

