（Optional）Write a program using nested loops that asks the user to enter a value for the number of rows to display. It should then display that many rows of asterisks, with one asterisk in the first row, two in the second row, and so on. For each row, the asterisks are preceded by the number of periods needed to make all the rows display a total number of characters equal to the number of rows. A sample run would look like this:
....
...
..
.****

The input consists of n (0<n<100) lines.
Each line consists of the number of rows(range from 1 to 100).
The last line of input consists of Int(-1).