#include <iostream>
#include <cstdio>
using namespace std;
const int N = 1e6 + 10;
int sum[N];
char a[N];
int main()
{
    int n;
    scanf("%d\n", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%c", &a[i]);
        if (a[i] == '0') sum[i] = sum[i - 1] + 1;
        else sum[i] = sum[i - 1] - 1;
    }
    for (int i = n; i >= 1; i--)
        for (int j = 1; j + i - 1 <= n; j++)
            if (sum[j + i - 1] == sum[j - 1])
            {
                printf("%d\n", i);
                return 0;
            }
    putchar('0');
    return 0;
}