测试点

#include <iostream>
using namespace std;
const int N = 1e5+5;
int pre[N];
int main()
{
	int n, num;
	int Len = 0;
	cin >> n;
	for (int i = 1; i <= n; i ++) {
		cin >> num;
		pre[i] = pre[i - 1] + num;
	}
	for (int i = 1; i <= n; i ++) {
		int j;
		if (!Len ) j = i + 1;
		else j = i + Len - 1;
		for ( ; j <= n; j += 2) {
			if ((j - i + 1) / 2 == pre[j] - pre[i - 1]) {
				Len = max(Len, j - i + 1);
			}
		}
	}
	cout << Len << endl;
	return 0;
}