Non-interactive Menu

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem Statement

A calculator receives a stream of command pairs (m, x). Initially total = 0. Command m = 1 adds x; command m = 2 subtracts x. Upon m = 0, stop and print only the final total. The terminating command is the pair 0 0 and has no effect on the total. Do not print any prompts or menu text.

Input

A sequence of integer pairs m x, separated by whitespace, where m belongs to {0,1,2}. The last pair is 0 0; previous commands have code 1 or 2. Operands may be negative, zero or positive.

Output

Print one integer: the final total, followed by a newline.

Subtasks

• Subtask 1 (20%): At most 5 pairs including 0 0; $|x|\le10$.
• Subtask 2 (30%): At most 100 pairs including 0 0; $|x|\le1000$.
• Subtask 3 (50%): At most 10000 pairs including 0 0; $|x|\le10^6$.

Examples

Example 1

Input

1 8
2 3
1 -4
0 0

Output

1

Explanation

Starting from 0: add 8 → 8, subtract 3 → 5, add -4 → 1; 0 0 stops processing.

Example 2

Input

0 0

Output

0

Explanation

The first command terminates the stream, so the unchanged total is zero.