Problem Description

You need to design a student record management system. At the beginning, the student record data is empty. Then the system must support the following operations (no more than $10^5$ operations in total):

• Insert and update, format 1 NAME SCORE: Insert a student whose name is $\texttt{NAME}$ (a case-sensitive string consisting of letters and digits, with at most $20$ characters) and whose score is $\texttt{SCORE}$ ($0<\texttt{SCORE}<2^{31}$). If a student with the same name already exists, update this student's score to $\texttt{SCORE}$. If the insertion or update succeeds, output OK.
• Query, format 2 NAME: Query the score of the student whose name is $\texttt{NAME}$. If the student cannot be found, output Not found; otherwise, output the student's score.
• Delete, format 3 NAME: Delete the information of the student whose name is $\texttt{NAME}$. If the student cannot be found, output Not found; otherwise, output Deleted successfully.
• Summary, format 4: Output the number of students in the system.

Input Format

The first line contains a positive integer $Q$ ($1 \le Q \le 10^5$), which indicates the number of operations.

In the next $Q$ lines, each line first contains a positive integer $op$ ($op \in [1,4]$), which indicates the type of operation. Then:

• If $op = 1$, input an additional string $\texttt{NAME}$ and a positive integer $\texttt{SCORE}$, with meanings as described above.
• If $op = 2$, input an additional string $\texttt{NAME}$, with meaning as described above.
• If $op = 3$, input an additional string $\texttt{NAME}$, with meaning as described above.
• If $op = 4$, no additional input is needed.

Output Format

Output a total of $Q$ lines. Each line outputs a string or a positive integer, which is the processing result of the corresponding operation. The exact meaning is as described above.

5
1 lxl 10
2 lxl
3 lxl
2 lxl
4

OK
10
Deleted successfully
Not found
0

Hint

Translated by ChatGPT 5