The Y Bus Goes Vroom

Interview

Time limit2sMemory limit256 MB

Summary

Simulate the passenger count as a bus travels N stops with given boarding and alighting numbers, then print the driver's fixed name.

Level: Easy1 of 10
Topics: Simulation, Implementation, Math
Solved: No attempts yet

Problem

The bus that driver 비와이 drives leaves the first station, passes $N$ stops, and arrives at the last station. Each stop has a fixed number of people who get off and a fixed number who get on. At the last station everyone still on the bus gets off.

Input

The first line has the number of stops between the first and the last station, $N$ ( $1 \le N \le 100\,000$ ), and the number of people who board at the first station, $K$ ( $1 \le K \le 10\,000$ ).

Each of the next $N$ lines has the number of people who board at the $i$ -th stop, $A$ , and the number of people who get off there, $B$ ( $0 \le A, B \le 10\,000$ ).

Output

Print the name of the bus driver at the moment the bus reaches the last station, on one line. Write the name in Hangul, exactly 비와이.

Examples2

Example 1
Input
```
3 2
10 3
21 8
0 15
```
Expected output
```
비와이
```
Example 2
Input
```
1 1
0 0
```
Expected output
```
비와이
```