#include <bits/stdc++.h>
using namespace std;
using lint = long long;
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V< V<T> >;

template<class Itr> auto rle(Itr first, Itr last) {
  V< pair<decltype(*first), int> > res;
  for (; first != last; ++first) {
    if (res.empty() or res.back().first != *first) {
      res.emplace_back(*first, 1);
    } else {
      ++res.back().second;
    }
  }
  return res;
}

int main() {
  cin.tie(nullptr); ios::sync_with_stdio(false);
  int n; cin >> n;
  V<> a(n); for (auto&& e : a) cin >> e;
  V<> dp(2);
  for (const auto& e : rle(begin(a), end(a))) {
    V<> ndp(2);
    ndp[0] = max(dp[0], dp[1]);
    ndp[1] = dp[0] + e.second;
    swap(dp, ndp);
  }
  cout << max(dp[0], dp[1]) << '\n';
}