#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
int sx[100005];
int sy[100005];
int a[100005]; 
int maxx=0;
int main(){
	freopen("teen.in","r",stdin);
	freopen("teen.out","w",stdout);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]==0){
			sy[i]=sy[i-1];
			sx[i]=sx[i-1]+1;
		}else{
			sx[i]=sx[i-1];
			sy[i]=sy[i-1]+1;
		}
	}
	for(int i=(n/2)*2;i>=2;i-=2){
		for(int j=1;j<=n-i+1;j++){
			int k=j+i-1;
			if(sx[k]-sx[j-1]==sy[k]-sy[j-1]){
				maxx=max(maxx,i);
				cout<<maxx;
				return 0;
			}
		}
	}
	cout<<maxx;
	fclose(stdin);
	fclose(stdout);
	return 0;
}