lines = []
while line = gets
    lines << line.chomp.split(' ').map(&:to_i)
end

N = lines[0][0]

b = []
for i in 1..N-1 do
  b.push(lines[1][i-1])
end

def min(x,y)
  if x > y then
    return y
  else
    return x
  end
end
  
ans = []
for i in 1..N do
  if i == 0 then
    ans.push(b[0])
  elsif i == N then
    ans.push(b[-1])
  else
    ans.push(min(b[i-2], b[i-1]))
  end
end
    
result = 0
for i in 1..N do
  result += ans[i-1]
end
print result