#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<queue>

using namespace std;

#define int long long
#define endl "\n"

const long long INF = (long long)1e18;
const long long MOD = 1'000'000'007; 

string yn(bool f){return f?"Yes":"No";}
string YN(bool f){return f?"YES":"NO";}



signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	const int MAX = 110'000;
	int N;
	int a = 0, b = 0;
	vector<int> A;
	vector<pair<int,int>> B;
	vector<vector<int>> dp;
	cin>>N;
	
	A.resize(N);
	
	for(int i = 0; i < N; i++){
		cin>>A[i];
		
		if(B.size() == 0) B.push_back({1,A[i]});
		else if(B.back().second == A[i]) B.back().first++;
		else B.push_back({1,A[i]});
	}
	
	dp.resize(2, vector<int>(B.size()+10));
	
	for(int i = 0; i < B.size(); i++){
	
		dp[0][i+1] = max(dp[0][i+1], dp[0][i]);
		dp[0][i+1] = max(dp[0][i+1], dp[1][i]);
		dp[1][i+1] = max(dp[1][i+1], dp[0][i]+B[i].first);
	}
	
	cout<<max(dp[1][B.size()], dp[0][B.size()])<<endl;
	
	
	return 0;
}