#include <bits/stdc++.h>

const int N = 2e5+10;
int n;
int a[N];

int findMax() {
    int ans = 0, res = 0;
    for (int i = 1; i <= n; ++ i) 
        ans = std::max(a[i], ans + a[i]), res = std::max(res, ans);
    return res;
}

int findMin() {
    int ans = 0, res = 0;
    for (int i = 1; i <= n; ++ i) 
        ans = std::min(a[i], ans + a[i]), res = std::min(res, ans);
    return res;
}

int main() {
    freopen("count1s.in", "r", stdin); 
    freopen("count1s.out", "w", stdout);
    std::cin >> n;
    for (int i = 1; i <= n; ++ i) std::cin >> a[i];
    for (int i = 1; i <= n; ++ i) a[i] = a[i] ? -1 : 1;
    std::cout << findMax() - findMin() + 1;
    return 0;
}