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

int main(){
   int n;
    cin >> n;
    vector<vector<int>> dp(n+1,vector<int>(2,0));

    for(int i = 1;i<=n;i++){
        int a;
        cin >> a;
        dp[i][0] = max(dp[i-1][0],dp[i-1][1]);
        dp[i][1] = dp[i-1][0] + a;
     }

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