#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int m = 1000000007;
const int Max = 1000;
int dp[100001][3];
int main()
{
int n;
cin>>n;
string s;
cin>>s;
dp[0][0] = dp[0][1] = dp[0][2] = 1;
for(int i = 1 ; i < s.length() ; i++){
dp[i][0] = dp[i-1][0] + (s[i]!=s[i-1]);
dp[i][1] = max(dp[i-1][0]+ (s[i] == s[i-1]) , dp[i-1][1] + (s[i] != s[i-1]) );
dp[i][2] = max(dp[i-1][2] + (s[i] != s[i-1]) , dp[i-1][1] + (s[i] == s[i-1]));
}
cout<<max(dp[n-1][0] ,max(dp[n-1][1], dp[n-1][2]))<<endl;
}
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