#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> v(n);
    int mx=0,zero=0,one=0,score=0;
    for (int i = 0; i < n; i++) {
        cin>>v[i];
        if(v[i]==0)++zero;
        else {
            ++one;
            ++score;
        }
        if(zero>one)
            mx=max(mx,zero-one);
        else {
            zero=0;
            one=zero;
        }
    }
    if(score+mx==score)cout<<score-1;
    else
    cout<<score+mx;
}