/* 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 a1[] ={1,5,3,21234};
		int a2[] = {4509,200,3,40};
		int dp[] = new int [a1.length];
		dp[0] = Math.max(Math.max(a1[0],a2[0]),0);
		dp[1] = Math.max(dp[1],Math.max(a1[1],a2[1]));
 
		for(int i = 2; i < a1.length; i++){
			dp[i] = Math.max(Math.max(a1[i],a2[i]) + dp[i-2],dp[i-1]);
		}
		System.out.println(dp[a1.length-1]);
		// your code goes here
	}
}

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