백준 2156

package baekjoon.DP;

import java.util.*;
import java.io.*;

class Main2156 {

   static int[] D, A;

   public static void main(String[] args) throws Exception {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st;
      int N = Integer.parseInt(br.readLine());
      D = new int[N + 1];
      A = new int[N + 1];
      for (int i = 1; i <= N; i++) {
         A[i] = Integer.parseInt(br.readLine());
      }
      // D[N] = max(D[N-1], (D[N-2]+A[N]) , (D[N-3] + +A[i-1] + A[N])
      if (N >= 1)
         D[1] = A[1];
      if (N >= 2)
         D[2] = D[1] + A[2];
      if (N >= 3)
         D[3] = Math.max(D[2], Math.max(D[1] + A[3], A[1] + A[3]));
      for (int i = 4; i <= N; i++) {
         D[i] = Math.max(D[i - 1], Math.max(D[i - 2], D[i - 3] + A[i - 1]) + A[i]);
      }

      System.out.println(D[N]);
   }
}