/* 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
	{
		// your code goes here
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int arr[]=new int[n];
		for(int i=0;i<n;i++) arr[i]=sc.nextInt();
		int b=sc.nextInt();
		int sum=0;
		for(int i=0;i<b;i++){
			sum=sum+arr[i];
		}
		int i=b,j=arr.length-1;
		int max=sum;
		while(i>=0 && j>i){
			sum=sum+arr[j]-arr[i];
			max=Math.max(max,sum);
			i--;
			j--;
		}
		System.out.println(max);
	}
}

LyogcGFja2FnZSB3aGF0ZXZlcjsgLy8gZG9uJ3QgcGxhY2UgcGFja2FnZSBuYW1lISAqLwoKaW1wb3J0IGphdmEudXRpbC4qOwppbXBvcnQgamF2YS5sYW5nLio7CmltcG9ydCBqYXZhLmlvLio7CgovKiBOYW1lIG9mIHRoZSBjbGFzcyBoYXMgdG8gYmUgIk1haW4iIG9ubHkgaWYgdGhlIGNsYXNzIGlzIHB1YmxpYy4gKi8KY2xhc3MgSWRlb25lCnsKCXB1YmxpYyBzdGF0aWMgdm9pZCBtYWluIChTdHJpbmdbXSBhcmdzKSB0aHJvd3MgamF2YS5sYW5nLkV4Y2VwdGlvbgoJewoJCS8vIHlvdXIgY29kZSBnb2VzIGhlcmUKCQlTY2FubmVyIHNjID0gbmV3IFNjYW5uZXIoU3lzdGVtLmluKTsKCQlpbnQgbiA9IHNjLm5leHRJbnQoKTsKCQlpbnQgYXJyW109bmV3IGludFtuXTsKCQlmb3IoaW50IGk9MDtpPG47aSsrKSBhcnJbaV09c2MubmV4dEludCgpOwoJCWludCBiPXNjLm5leHRJbnQoKTsKCQlpbnQgc3VtPTA7CgkJZm9yKGludCBpPTA7aTxiO2krKyl7CgkJCXN1bT1zdW0rYXJyW2ldOwoJCX0KCQlpbnQgaT1iLGo9YXJyLmxlbmd0aC0xOwoJCWludCBtYXg9c3VtOwoJCXdoaWxlKGk+PTAgJiYgaj5pKXsKCQkJc3VtPXN1bSthcnJbal0tYXJyW2ldOwoJCQltYXg9TWF0aC5tYXgobWF4LHN1bSk7CgkJCWktLTsKCQkJai0tOwoJCX0KCQlTeXN0ZW0ub3V0LnByaW50bG4obWF4KTsKCX0KfQ==

NQo1IC0yIDMgMSAyCjM=

5
5 -2 3 1 2
3