#include <iostream>
#include <string>

using namespace std;


int main()
{
	bool f=false;
	int res=INT_MIN;
	string s;
	int curLen=0,maxLen=-1,maxInd=-1;
	int i,ind,k;
	char c;
	cin>>k;
	cin>>s;
	for (i=1;i<s.size();i++)
	{
		if (!f && s[i]==s[i-1])
		{
			f=true;
			ind=i;
			curLen=1;
			continue;
		}
		if (f && s[i]!=s[i-1])
		{
			curLen++;
			continue;
		}
		if (f && s[i]==s[i-1])
		{
			if (curLen>maxLen)
			{
				maxLen=curLen;
				maxInd=ind;
			}
			curLen=1;
			ind=i;
			continue;
		}
	}
	if (f)
		if (curLen>maxLen)
			{
				maxLen=curLen;
				maxInd=ind;
			}

	if (maxInd!=-1)
		for (i=maxInd;i<maxInd+maxLen;i++)
		{
			if (s[i]=='0')
				s[i]='1';
			else
				s[i]='0';
		}
	c='1';
	curLen=0;
	for (i=0;i<s.size();i++)
	{
		if (s[i]!=c)
		{
			curLen++;
			c=s[i];
		}
	}
	res=max(res,curLen);
	c='0';
	curLen=0;
	for (i=0;i<s.size();i++)
	{
		if (s[i]!=c)
		{
			curLen++;
			c=s[i];
		}
	}
	res=max(res,curLen);
	cout<<res;
}