n = int(input())
a = list(map(int, input().split()))
for i in range(1, n-1):
if a[i-1] == 1 and a[i] == 0 and a[i+1] == 1:
a[i] = 1
wynik = a.count(1)
print(wynik)# your code goes here
biA9IGludChpbnB1dCgpKQphID0gbGlzdChtYXAoaW50LCBpbnB1dCgpLnNwbGl0KCkpKQoKZm9yIGkgaW4gcmFuZ2UoMSwgbi0xKToKCWlmIGFbaS0xXSA9PSAxIGFuZCBhW2ldID09IDAgYW5kIGFbaSsxXSA9PSAxOgoJCWFbaV0gPSAxCnd5bmlrID0gYS5jb3VudCgxKQpwcmludCh3eW5paykjIHlvdXIgY29kZSBnb2VzIGhlcmU=