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


int dp[1010][2];
int N;
int v[10000];

int rec(int n, int k){
    if (dp[n][k] > -1) return dp[n][k];
    dp[n][1] = rec(n - 1,0) + v[n - 1];
    dp[n][0] = max(rec(n - 1, 0),rec(n- 1, 1));

        
    return dp[n][k];
}

int main(){
    cin >> N;
    for (int i = 0; i < N; ++i){
        cin >> v[i];
    }
    memset(dp, -1, sizeof(dp));
    dp[0][0] = dp[0][1] = 0;
    int res = max( rec(N,0), rec(N, 1));
    cout << res << endl;
    
}