Minimum Maximum Subarray Sum (Java)

import java.util.*;

class TestClass {
    public static void main(String args[] ) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = sc.nextInt();

        long l = 1, r = (long)1e15, m;
        while (l < r) {
            m = (l + r) / 2;

            if (numberOfSubarrays(a, m) <= k)
                r = m;
            else
                l = m + 1;
        }

        System.out.println(r);
    }

    static int numberOfSubarrays(int[] a, long sum) {
        int ans = 0;
        long curr = 0;
        for (int x : a) {
            if (x > sum)
                return Integer.MAX_VALUE; // Not possible
            if (curr + x > sum) {
                ans++;
                curr = 0;
            }
            curr += x;
        }

        return ans + 1;
    }
}