#include <bits/stdc++.h>
#define pb emplace_back
using namespace std;
const int maxn = 2e5 + 5;
int n,a[maxn];
vector<int> g;
int main() {
    freopen("count1s.in","r",stdin);
    freopen("count1s.out","w",stdout);
    scanf("%d",&n);
    int tot = 0;
    for(int i = 1;i <= n;++ i)scanf("%d",&a[i]),tot += a[i];
    int cnt = 1;
    for(int i = 2;i <= n;++ i) {
        if(a[i] != a[i - 1]) {
            g.pb(cnt * (-a[i - 1] * 2 + 1));
            cnt = 1;
        }
        else ++ cnt;
    }
    g.pb(cnt * (-a[n] * 2 + 1));
    cnt = 0;
    int mx = 0,mn = 0;
    for(auto v : g) {
        if(cnt < 0)cnt = v;
        else cnt += v;
        mx = max(mx , cnt);
    }
    cnt = 0;
    for(auto v : g) {
        if(cnt > 0)cnt = v;
        else cnt += v;
        mn = min(mn , cnt);
    }
    printf("%d\n",mx - mn + 1);
    fclose(stdin);
    fclose(stdout);
    return 0;
}