#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>
#include <iomanip>
#include <stack>
#include <queue>
#include <numeric>
#include <map>
#include <unordered_map>
#include <set>
#include <fstream>
#include <chrono>
#include <random>
#include <bitset>
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define mod 1000000007
using ll = long long;
using namespace std;
ll gcd(ll a, ll b) {return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) {return a/gcd(a,b)*b;}

int main(){
  int N; cin >> N;
  vector<int> V(N); rep(i,N) cin >> V[i];
  vector<int> dp0(N+1,0);
  vector<int> dp1(N+1,0);
  for(int i=1; i<=N; i++){
    dp0[i] = max(dp0[i-1],dp1[i-1]);
    dp1[i] = dp0[i-1]+V[i-1];
  }
  cout << max(dp0[N],dp1[N]) << endl;
  return 0;
}