n=int(input())
b=list(map(int,input().split()))
a=[]
ans=b[0]
a.append(ans)
for i in range(1,n-1):
    if(b[i] < ans):
        a.append(b[i])
    else:
        a.append(ans)
    ans=b[i]
a.append(b[i])
print(sum(a))