n=int(input())
a=list(map(int,input().split()))
ans=0
for i in range(n-1):
    tmp=1
    if a[i]==1:
        ans+=1
        for j in range(i+1,n-1):
            if tmp==1 and a[j]==0:
                tmp=0
                ans+=1
            elif tmp==0 and a[j]==1:
                tmp=1
                ans+=1
            else :
                break
print(ans)