1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 int a[100001],Map[200001],sum[200001],n,i,ans;
 5 int main(){
 6     scanf("%d",&n);
 7     for(i=1;i<=n;i++){
 8         scanf("%d",&a[i]); if(a[i]==0)a[i]=-1; sum[i]=sum[i-1]+a[i];
 9     }
10     for(i=1;i<=n;i++){
11         if(sum[i]==0){ans=max(ans,i);continue;}
12         if(Map[sum[i]+n]&&ans<i-Map[sum[i]+n])
13             ans=i-Map[sum[i]+n];
14         if(Map[sum[i]+n]==0)
15             Map[sum[i]+n]=i;
16     }
17     cout<<ans<<endl;
18 }