#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 = 110000;
	int N;
	int a = 0, b = 0;
	vector<int> A, used;
	vector<pair<int,int>> B;
	static int dp[MAX] = {};
	priority_queue<pair<int,int>> Q;
	
	cin>>N;
	
	A.resize(N);
	used.resize(N+10);
	
	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]});
	}
	
	// for(int i = 0; i < B.size(); i++){ //cout<<i<<endl;
		// if(i%2) a += B[i].first;
		// else b += B[i].first;
	// }
	
	for(int i = 0; i < B.size(); i++){
		// for(int ){
		// }
		
		// Q.push(make_pair(B[i].first,i+1));
	}
	
	
	// while(!Q.empty()){
		// pair<int,int> P = Q.top(); Q.pop();
		// int con = P.second;
		
		// if(used[con]) continue;
		
		// used[con+1] = true;
		// used[con] = true;
		// used[con-1] = true;
		
		// a += P.first;
	// }
	
	for(int i = 0; i < B.size(); i++){
		dp[i+2] = max(dp[i+2], B[i].first+dp[i]);
		dp[i+1] = max(dp[i+1], dp[i]);
		a = max(dp[i], dp[i+1]);
		a = max(dp[i], dp[i+2]);
	}
	
	cout<<max(a,b)<<endl;
	
	
	return 0;
}