#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

#define RREP(i,s,e) for (i = e-1; i >= s; i--)
#define rrep(i,n) RREP(i,0,n)
#define REP(i,s,e) for (i = s; i < e; i++)
#define rep(i,n) REP(i,0,n)
#define INF 1e8

typedef long long ll;

int main() {
    int i, n;
    int v[1000];
    int dp[1001][2];
    cin >> n;
    rep (i,n) cin >> v[i];
    rep (i,n) {
        dp[i+1][0] = max(dp[i][0],dp[i][1]);
        dp[i+1][1] = dp[i][0] + v[i];
    }
    cout << max(dp[n][0],dp[n][1]) << endl;
    return 0;
}