#include<iostream>
#include<cstdio>
using namespace std;
int n,a[100010],s[100010],l[210000],r[210000],ans,ma,delta;
int main()
{
	freopen("teen.in","r",stdin);
    freopen("teen.out","w",stdout);
	scanf("%d",&n);
	delta=n;
	for(int i=1;i<=n;i++)
	{
		scanf("%d",&a[i]);
		if(a[i]==0) a[i]=-1;
	}
	for(int i=1;i<=n;i++)
	{
		s[i]=s[i-1]+a[i];
	    if(l[s[i]+delta]==0&&s[i]+delta!=n) l[s[i]+delta]=i;
	    r[s[i]+delta]=i;
    }
    for(int i=0;i<=2*n;i++)
    {
    	ans=max(ans,r[i]-l[i]);
	}
	printf("%d",ans);
	return 0;
 }