#include <bits/stdc++.h>
using namespace std;
const int N = 200010;

int n,a[N],sa,sb,l[N],r[N];//a男b女,lr记录差值为下标时的左右端点 
int ans;

int main(){
	freopen("teen.in","r",stdin);
	freopen("teen.out","w",stdout); 
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
		sa+=(1==a[i]);
		sb+=(0==a[i]);
		int t=sa-sb+n;
        if (!l[t]&&t!=n) l[t]=i; else r[t]=i; 
	}
	for (int i=0;i<=2*n;i++) ans=max(ans,r[i]-l[i]);
    cout<<ans<<endl;
	return 0; 
}