Week of Tsinghua

You are given an integer d, the 1-indexed number of days since 2025-01-01 (inclusive). That is:

• d = 1 means 2025-01-01
• d = 2 means 2025-01-02
• and so on.

Determine the academic week number in Tsinghua University’s academic calendar for the date represented by d.

The input date is guaranteed to be within the calendar range:

• from 2025-08-20 to 2026-02-23 (inclusive).

Calendar Rules

• Week 1 starts on 2025-09-15 (Monday).
• Each academic week is Monday to Sunday.
• There are 18 weeks in every semester, and holidays still count toward the week number.
• If the date is before 2025-09-15, output 0.
• If the date is during winter break, output 19.

Input

One line with one integer: d.

Output

One line with a single integer:

• 0 if not started yet,
• 1..18 for teaching weeks,
• 19 if already on winter break.

Sample

Input

357

Output

15

Explanation: t = 357 corresponds to 2025-12-23, which falls in Week 15.