#include <iostream>
#include <vector>

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> a(n + 1, 0);
    vector<int> sum(n + 1, 0);
    vector<int> res;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
        if (a[i] == 0) {
            a[i] = -1;
        }
    }
    for (int i = 1; i <= n; ++i) {
        sum[i] = sum[i - 1] + a[i];
    }
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n; ++j) {
            if (sum[i] - sum[j] == 0) {
                res.emplace_back(j - i);
            }
        }
    }
    int ans = -1;
    for (int i = 1; i <= res.size(); ++i) {
        ans = max(ans, res[i]);
    }
    cout << ans << endl;
    return 0;
}