PROGRAMMING:Stick wall "triangle"
###Task description
```
Input some positive integers (≤ 26), and program to output the letter triangle attached to the wall with these positive integers as the side length.
```
###Input format:
```
Several positive integers
```
###Output format:
```
The pattern corresponding to each positive integer. There is a blank line between each group of patterns.
```
###Input example:
```in
three
seven
```
###Output example:
```out
a a
a ab
aabc
a a
a ab
a abc
a abcd
a abcde
a abcdef
aabcdefg
```
###Title Source
Selected from openjudge website, online address: http://sdau.openjudge.cn/17lx3/13/
answer：If there is no answer, please comment
```
Input some positive integers (≤ 26), and program to output the letter triangle attached to the wall with these positive integers as the side length.
```
###Input format:
```
Several positive integers
```
###Output format:
```
The pattern corresponding to each positive integer. There is a blank line between each group of patterns.
```
###Input example:
```in
three
seven
```
###Output example:
```out
a a
a ab
aabc
a a
a ab
a abc
a abcd
a abcde
a abcdef
aabcdefg
```
###Title Source
Selected from openjudge website, online address: http://sdau.openjudge.cn/17lx3/13/
answer：If there is no answer, please comment