/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		int n = 6;
		int[] a = {10, -50, -20, 10, 100, -10, 20}; 
 
		long[] dp = new long[n + 1];
		long kk = 0;
 
		dp[1] = Math.max(a[1], kk);
 
		dp[2] = Math.max(a[2], dp[1]);
 
		int i = 3;
		while (i <= n) {
			dp[i] = Math.max(a[i] + dp[i - 2], dp[i - 1]);
			i++;
		}
 
		System.out.println(dp[n]);
 
	}
}

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