70分求大佬帮我看一看！！！（必关）

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

int n, na[100015], v[100015], ans;
bool a[100015];
signed main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        na[i] = na[i - 1] + !a[i];
        v[i] = v[i - 1] + a[i];
    }
    for (int i = 1; i < n; i++) {
        for (int j = i + 1; j <= n; j++) {
            int x = na[j] - na[i - 1];
            int y = v[j] - v[i - 1];
            if (x == y) {
                ans = max(ans, x + y);
            }
        }
    }
    cout << ans;
    return 0;
}