N = int(input())
A = list(map(int, input().split()))

import re


def get_idxs(string, word):
    idxs = []

    for res in re.finditer(word, string):
        idxs.append(res.span()[0])

    return idxs


inds = get_idxs("".join(map(str, A)), "1")

ans = [0] * len(inds)
for i in range(len(inds))[::-1]:
    if i == len(inds) - 1:
        if inds[i] == N - 1:
            continue
        elif inds[i] == N - 2:
            ans[i] = 1
        else:
            ans[i] = 2
    else:
        if inds[i] + 2 == inds[i + 1]:
            ans[i] += 2 + ans[i + 1]
        elif inds[i] + 1 == inds[i + 1]:
            ans[i] = 1
        else:
            ans[i] = 2

print(sum(ans))