Two-Heap Gifts

**Description:** You receive n gifts in order, gift i worth w_i. After each receipt, **while you hold more than one gift**, immediately give away the smallest-valued gift you hold. After all n steps, print the total worth of the gifts you still hold. **Input:** Line 1: n (1 <= n <= 2*10^5). Line 2: n integers w_i (|w_i| <= 10^9). **Output:** One integer — the total worth of kept gifts. **Example:** 4 / 3 1 4 2 -> 4 (+3 hold {3}; +1 give 1, hold {3}; +4 give 3, hold {4}; +2 give 2, hold {4}).