#include<bits/stdc++.h>
int n,m,k,s,t,ans;
int a[100001],sum[100001],first[200001],last[200001];
int main()
{
    std::cin>>n;
    memset(first,-1,sizeof(first));
    memset(last,-1,sizeof(last));
    sum[0]=n;
    first[n]=last[n]=0;
    for(int i=1;i<=n;i+=1)
    {
        std::cin>>a[i];
        if(!a[i])a[i]=-1;
        sum[i]=sum[i-1]+a[i];
        if(first[sum[i]]==-1)first[sum[i]]=i;
        last[sum[i]]=i;
    }
    for(int i=0;i<=2*n;i+=1)if(first[i]!=-1)ans=std::max(ans,last[i]-first[i]);
    std::cout<<ans;
}

#include <bits/stdc++.h>
using namespace std;
int n, a[100005], sum[100005], first[200005], last[200005], ans;
int main()
{
    cin >> n;
    memset(first, -1, sizeof(first));
    memset(last, -1, sizeof(last));
    sum[0] = n;
    first[n] = last[n] = 0;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
        if (!a[i])
        {
            a[i] = -1;
        }
        sum[i] = sum[i - 1] + a[i];
        if (first[sum[i]] == -1)
        {
            first[sum[i]] = i;
        }
        last[sum[i]] = i;
    }
    for (int i = 0; i <= 2 * n; i++)
    {
        if (first[i] != -1)
        {
            ans = max(ans, last[i] - first[i]);
        }
    }
    cout << ans;
    return 0;
}