#include <iostream>
using namespace std;

int dp[2][1005];

int main(){
    int n;
    cin >> n;

    int v;

    for(int i=1; i<=n; i++){
        cin >> v;

        if(i == 1){
            dp[0][1] = v;
            dp[1][1] = 0;
            continue;
        }

        dp[0][i] = dp[1][i-1] + v;
        dp[1][i] = max(dp[0][i-1], dp[1][i-1]);
    }

    cout << max(dp[0][n], dp[1][n]) << endl;
}