#include <bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0;i < n;i++){
        cin >> a[i];
    }

    vector<pair<int, int>> pa;
    pa.push_back({a[0], 1});
    int size = 1;

    for(int i = 1;i < n;i++){
        if(pa[size-1].first == a[i]){
            pa[size-1].second++;
        }else{
            pa.push_back({a[i], 1});
            size++;
        }
    }

    int dp[100010];
    dp[0] = pa[0].second;
    if(1 < size){
        dp[1] = max(dp[0], pa[1].second+dp[0]-1);
        for(int i = 2;i < size;i++){
            dp[i] = max(dp[i-1]-1+pa[i].second, dp[i-2]+pa[i].second);
        }
    }

    cout << dp[size-1] << endl;

    return 0;
}