Create q002.md for Accumulator Apex problem

Added problem statement and details for 'Accumulator Apex'.

Author: Dheeraj-06

Problems/Data-structures/Day-04/q002.md

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+# 🧮 Accumulator Apex
+
+**Problem Link:**  
+🔗 https://codeforces.com/problemset/problem/1912/A
+
+**Time Limit:** 3 seconds  
+**Memory Limit:** 1024 MB
+
+---
+
+## 📘 Problem Statement
+
+Allyn is playing a new strategy game called **Accumulator Apex**.
+
+In this game:
+
+- Allyn is given an initial integer value **x**, called the **accumulator**.
+- There are **k** lists of integers.
+- Allyn can make multiple turns.
+
+### 🔁 Game Rules
+
+On each turn, Allyn can:
+
+- Choose **any non-empty list**
+- Withdraw the **leftmost element** from that list
+- Add it to the accumulator **x**, **only if** the resulting value of **x** is **non-negative**
+
+Allyn may **end the game at any moment**.
+
+---
+
+## 🎯 Objective
+
+Find the **maximum possible value** of the accumulator **x** that Allyn can achieve.
+
+---
+
+### 📥 Input Format
+
+The first line contains two integers **x** and **k**:
+
+- $0 \le x \le 10^9$
+- $1 \le k \le 10^5$
+
+The next **k** lines describe the lists:
+
+- Each line starts with an integer **lᵢ** $(lᵢ \ge 1)$
+- Followed by **lᵢ** integers representing the list elements (from left to right)
+
+---
+
+### 🔢 Constraints
+
+- Each element in the lists satisfies:  
+  $|a_{ij}| \le 10^9$
+
+- The total number of elements across all lists does not exceed:  
+  $10^5$
+
+---
+
+## 📤 Output Format
+
+- Print a single integer — the **maximum possible value** of the accumulator **x**.
+
+---
+
+## 📝 Notes
+
+- Elements must be taken **from the left end** of a list.
+- You can switch between lists at any time.
+- You are **not required** to consume all elements.
+- The accumulator value must **never become negative**.
+
+---
+
+## ✅ Example (Conceptual)
+
+If at some point adding an element makes the accumulator negative, that move is **not allowed**.
+
+The optimal strategy may involve:
+- Taking positive elements early
+- Skipping lists that block progress due to large negative prefixes
+
+---
+
+## 🏁 End of Problem