#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
/*
 *
 * no changes
 *
int maxOnes(const vector<int>& v) {
    int n = v.size();
    int left = 0;
    int right = 0;
    int ans = 0;
    while (right < n) {
        left = right;
        while (right < n && v[right] == 1) {
            right++;
        }
        ans = max(ans, right - left);
        right++;
    }
    return ans;
}
 */

int maxOnes(const vector<int>& v) {
    size_t n = v.size();
    // n > 0

    // only ones no zeros
    if (count(v.begin(), v.end(), 1) == n) {
        return n - 1;
    }

    int ans = -1;
    int cur_zero_idx = -1;
    bool has_zero = false;
    int left = 0;
    int right = 0;

    while (right < n) {
        while (right < n && v[right] == 1) {
            ++right;
        }
        if (right < n) {
            has_zero = true;
            cur_zero_idx = right;
            right++; // delete zero
            while (right < n && v[right] == 1) {
                ++right;
            }
        }
        ans = max(ans, right - left);
        if (has_zero) {
            left = right = cur_zero_idx + 1; // next pos after current zero
            has_zero = false;
        }
    }

    return ans;
}

int main() {

    cout << maxOnes({0, 0, 1, 0, 1, 0, 0, 0, 0}) << endl;
    cout << maxOnes({1, 1, 1, 1}) << endl;
    cout << maxOnes({0, 0, 1, 1}) << endl;
    cout << maxOnes({1, 1, 1, 1, 0, 0, 0, 0, 0}) << endl;
    cout << maxOnes({0, 0, 0}) << endl;
    cout << maxOnes({1}) << endl;
    cout << maxOnes({1, 1, 1, 0, 1, 1}) << endl;
    cout << maxOnes({1,1,1,1, 0,0,0,0,0,1,1,1,1,1,1}) << endl;
    cout << maxOnes({1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1}) << endl;
    cout << maxOnes({1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1}) << endl;

    return 0;
}