#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <time.h>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<29;

const ld eps=1e-6;
const LL mod=1e+6 + 3;

int N, V[1024];
LL memo[1024][2];

LL rec(int n, int k){
	if(memo[n][k] != -1)
		return memo[n][k];
	if(n >= N)
		return 0;

	LL res = rec(n + 1, 0);
	if(!k){
		res = max(rec(n + 1, 1) + V[n], res);
	}
	return memo[n][k] = res;
}

int main() {
	cin.tie(0);
    ios::sync_with_stdio(false);
    memset(memo, -1, sizeof(memo));
    
    cin >> N;
    REP(i,N)
    	cin >> V[i];
    	
    cout << rec(0, 0) << endl;
 	return 0;
}