Split Without Overload

**Bài toán.** Split an ordered list of n jobs into at most k consecutive groups so that the largest group sum is minimized. Print that minimized maximum. **Constraints:** 1 ≤ k ≤ n ≤ 100000; 1 ≤ a[i] ≤ 10^9. **Output:** one integer. Feasibility is monotone in the answer — exploit it.