#include <bits/stdc++.h>
using namespace std; 
const int maxn=1e6 + 10;
int a[maxn],sum[maxn],index[2 * maxn];
int main() { 
   int n; 
   scanf("%d",&n); 
   sum[0]=0;
   memset(index,-1,sizeof(index));
   for (int i = 1; i <= n; ++i) 
   {
   	scanf("%d", &a[i]); 
   	if (a[i] == 0) 
   	a[i] = -1; 
   	sum[i] = sum[i - 1] + a[i]; 
   	int x = sum[i] + 1e6;
   	if (index[x] == -1)
   	index[x] = i;
   }
   int ans=0; 
   for(int i=2;i<=n;++i)
   {
   	int x=sum[i]+1e6;
   	ans=max(ans,i-index[x]);
   }
   cout<<ans;
   return 0;
}