Problem Description

Little B enjoys learning programming. He has already completed $x$ problems. In the upcoming period, Little B can solve either 1 or 2 programming problems each day. What is the minimum number of days required for Little B to complete at least $y$ problems?

Input Format

The input consists of two integers $x$ and $y$ on a single line.

Output Format

Output a single integer on a line, representing the minimum number of days.

Sample Input and Output

Sample Input #1

3 6

Sample Output #1

2

Sample Input #2

4 10

Sample Output #2

3

Sample Input #3

4 135428

Sample Output #3

67712

Notes

Data Size and Constraints

• For $20\%$ of the test cases, $1 \leq x < y \leq 10$;
• For $60\%$ of the test cases, $1 \leq x < y \leq 10^6$;
• For $100\%$ of the test cases, $1 \leq x < y \leq 10^{18}$.

见题面 Input 部分

见题面 Output 部分