241109-2156.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        int[] arr = new int[n + 1];
        int[] dp = new int[n + 1];
        for (int i = 1; i <= n; i++) {
            arr[i] = Integer.parseInt(br.readLine());
        }
        dp[0] = arr[0];
        dp[1] = arr[1];
        if (n == 1) {
            System.out.print(dp[1]);
            return;
        }
        dp[2] = arr[1] + arr[2];
        if (n == 2) {
            System.out.print(dp[2]);
            return;
        }

        for (int i = 3; i <= n; i++) {
            dp[i] = Math.max(dp[i - 1], Math.max(dp[i - 2] + arr[i], dp[i - 3] + arr[i - 1] + arr[i]));
        }
        System.out.print(Math.max(dp[n - 1], dp[n]));
    }
}