코드
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
public class Main {
static Integer[] dp;
static int[] arr;
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int N = Integer.parseInt(br.readLine());
dp = new Integer[N + 1];
arr = new int[N + 1];
for (int i = 1; i <= N; i++) {
arr[i] = Integer.parseInt(br.readLine());
}
dp[0] = 0;
dp[1] = arr[1];
if (N > 1) {
dp[2] = arr[1] + arr[2];
}
System.out.println(recur(N));
}
static int recur(int n) {
if (dp[n] == null) {
dp[n] = Math.max(recur(n - 1), Math.max(recur(n - 2), recur(n - 3) + arr[n - 1]) + arr[n]);
}
return dp[n];
}
}