#include<bits/stdc++.h>
using namespace std;
const double pi=3.14;
const int inf=0x3f3f3f3f;
const int NIL=-1;
const int MOD=1e9+7;
#define f(i,l,r) for(int i=l;i<=r;i++)
int n;
int a[200010],tot0[200010],tot1[200010],cost[200010];
int read()
{
    int ans=0,flag=1;
    char ch=getchar();
    while( (ch>'9' || ch<'0') && ch!='-' ) ch=getchar();
    if(ch=='-') flag=-1,ch=getchar();
    while(ch>='0' && ch<='9') ans=ans*10+ch-'0',ch=getchar();
    return ans*flag;
}
int main()
{
	freopen("count1s.in","r",stdin);
	freopen("count1s.out","w",stdout);
	tot0[0]=tot1[0]=0;
	cin>>n;
	for (int i=1;i<=n;i++){
		cin>>a[i];
		if (a[i]==0) tot0[i]++;
		else tot1[i]++;
		tot0[i]+=tot0[i-1];
		tot1[i]+=tot1[i-1];
		cost[i]=tot0[i]-tot1[i];
	}
	int minn=inf,maxx=-inf,minnans=inf,maxxans=-inf;
	for (int i=0;i<=n;i++){
		minn=min(minn,cost[i]);
		maxx=max(maxx,cost[i]);
		minnans=min(minnans,cost[i]-maxx);
		maxxans=max(maxxans,cost[i]-minn);
	}
	int l=tot1[n]+minnans,r=tot1[n]+maxxans;
	cout<<r-l+1<<endl;
}