#30032: python解答
carter921105@gmail.com
(Ted Carter)
n=int(input())
h=0
a=list(map(int,input().split()))
if(a[0]==0):
a[0]=a[1]
h=h+a[0]
if(a[n-1]==0):
a[n-1]=a[n-2]
h=h+a[n-2]
for i in range(1,n):
if(a[i]==0):
a[i]=min(a[i-1],a[i+1])
h=h+a[i]
print(h)
elif(a[n-1]!=0):
for i in range(1,n):
if(a[i]==0):
a[i]=min(a[i-1],a[i+1])
h=h+a[i]
print(h)
elif(a[0]!=0):
if(a[n-1]==0):
h=h+a[n-2]
for i in range(1,n-1):
if(a[i]==0):
a[i]=min(a[i-1],a[i+1])
h=h+a[i]
print(h)
elif(a[n-1]!=0):
for i in range(n):
if(a[i]==0):
a[i]=min(a[i-1],a[i+1])
h=h+a[i]
print(h)