input_lines = gets.chop.split.map(&:to_i)
input_lines2 = gets.chop.split.map(&:to_i)

count = input_lines2[0]
n = input_lines[0]

for i in 1...(n - 1)
    if input_lines2[(i - 1)] > input_lines2[i]
        count = count + input_lines2[i]
    else
        count = count + input_lines2[(i - 1)]
    end
end
count = count + input_lines2[(n-2)]
puts count