#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define N 100000
#define MAXN 200010
inline ll read(){
	ll x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
ll n,ans;
ll a[MAXN],sum[MAXN];//sum男生人数减女生人数 
ll mp[MAXN];
int main(){
	freopen("teen.in","r",stdin);
	freopen("teen.out","w",stdout);
	n=read();
	sum[1]=N;
	mp[N]=1;
	for(int i=2;i<=n+1;i++){
		a[i]=read();
		if(a[i]==0)sum[i]=sum[i-1]-1;
		else sum[i]=sum[i-1]+1;
		if(mp[sum[i]])ans=max(ans,i-mp[sum[i]]);
		else mp[sum[i]]=i;
//		cout<<sum[i]<<" ";
	}
	cout<<ans;
	return 0;
}