PROGRAMMING:String input exercise (III)
The substring of the output string.
###Input format:
Each line begins with a positive integer k, followed by a string s, separated by spaces（ Please write the input format here. For example: input 2 integers a and B with absolute value no more than 1000 in one line.
###Output format:
Output a substring of length k starting from the beginning.
###Input example:
```in
2 hello world!
```
###Output example:
```out
he
```
answer：If there is no answer, please comment
###Input format:
Each line begins with a positive integer k, followed by a string s, separated by spaces（ Please write the input format here. For example: input 2 integers a and B with absolute value no more than 1000 in one line.
###Output format:
Output a substring of length k starting from the beginning.
###Input example:
```in
2 hello world!
```
###Output example:
```out
he
```
answer：If there is no answer, please comment