Painters Partition Problem

#1

I cant find wrong in my solution, why is it not working for some test cases, please help me resolve it, I am pasting my code here:

import java.util.*;
public class Main {
public static void main(String args[]) {

	Scanner sc = new Scanner(System.in);
	int n  = sc.nextInt();
	int b = sc.nextInt();
	long[] boards = new long[b];
	long sum = 0;

	for(int i=0;i<b;i++){
		boards[i] = Math.abs(sc.nextInt());
		sum += boards[i];
	}

	Arrays.sort(boards);

	System.out.print(binarySearch(boards[b-1],sum,n,boards));

}

public static long binarySearch(long lo,long hi,long n, long[] arr){

	long result = -1;
	long mid = 0;

	while(lo<hi){
		mid = (lo+hi)/2;
		if(isPossible(mid,n,arr)){
			result = mid;
			hi = mid;
		}else{
			lo=mid+1;
		}
	}
	
    return result;
}

public static boolean isPossible(long m,long n,long[] arr){
	long painters = 1;
	long pbc = 0;

	for(int i=0;i<arr.length;i++){
		if(pbc+arr[i]<=m){
			pbc+=arr[i];
		}else{
			painters++;
			if(painters>n){
				return false;
			}
			pbc = arr[i];
		}	
	}

	return true;
}

}