N = int(eval(input()))

B =list(map(int,input().split()))

A=[0]*N



A[0]=B[0]

for i in range(1,N-1):

    A[i]=min(B[i],B[i-1])

A[-1]=B[-1]

print((sum(A)))
import sys

input = sys.stdin.readline



def I(): return int(eval(input()))

def MI(): return list(map(int, input().split()))

def LI(): return list(map(int, input().split()))



def main():

    mod=10**9+7

    N=I()

    B=LI()

    A=[0]*N

    A[0]=B[0]

    A[-1]=B[-1]

    for i in range(N-2):

        A[i+1]=min(B[i],B[i+1])

        

    print((sum(A)))



main()

N = int(eval(input()))
B = list(map(int, input().split()))
A = [0] * N
A[0] = B[0]
for i in range(1, N - 1):
    A[i] = min(B[i], B[i - 1])
A[-1] = B[-1]
print((sum(A)))

import sys

input = sys.stdin.readline


def I():
    return int(eval(input()))


def MI():
    return list(map(int, input().split()))


def LI():
    return list(map(int, input().split()))


def main():
    mod = 10**9 + 7
    N = I()
    B = LI()
    A = [0] * N
    A[0] = B[0]
    A[-1] = B[-1]
    for i in range(N - 2):
        A[i + 1] = min(B[i], B[i + 1])
    print((sum(A)))


main()

-N = int(eval(input())) -B = list(map(int, input().split())) -A = [0] * N -A[0] = B[0] -for i in range(1, N - 1): -    A[i] = min(B[i], B[i - 1]) -A[-1] = B[-1] -print((sum(A))) +import sys + +input = sys.stdin.readline + + +def I(): +    return int(eval(input())) + + +def MI(): +    return list(map(int, input().split())) + + +def LI(): +    return list(map(int, input().split())) + + +def main(): +    mod = 10**9 + 7 +    N = I() +    B = LI() +    A = [0] * N +    A[0] = B[0] +    A[-1] = B[-1] +    for i in range(N - 2): +        A[i + 1] = min(B[i], B[i + 1]) +    print((sum(A))) + + +main()