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

public class Main {

    public static void main (String[] args) throws java.lang.Exception {
        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();
      if(B>n){
        System.out.print(-1);
        return;
      }
        long sum = 0;
        for (int i = 0; i < n; i++) {
            sum = sum + arr[i];
        }
        long li = arr[0];
        long hi = sum+100;
        long res = -1;
        while (li <= hi) {
            long mid = (hi + li) / 2;
            if (isAllocationPossible(arr, n, B, mid)) {
                res = mid;
                hi = mid - 1;
            } else {
                li = mid + 1;
            }
        }
        System.out.println(res);
    }
    public static boolean isAllocationPossible(int [] arr, int n, int B, long barrier) {
        int student = 1;
        long currentpages = 0;
        for (int i = 0; i < n; i++) {
            if (arr[i] > barrier) {
                return false;
            }
            if (currentpages + arr[i] > barrier) {
                student++;
                if (student > B) {
                    return false;
                }
                currentpages = arr[i];
            } else {
                currentpages = currentpages + arr[i];
            }
        }
        return true;

    }
}