Hw4e3: you can approximate $\pi$ by using the following summation:
$\pi = 4 \times (1 - \frac{1}{3} + \frac{1}{5} - \frac{1}{7} + \frac{1}{9} - \dots + \frac{(-1)^{i+1}}{2i - 1})$
Write a program that prompt for and read from the keyboard the value of $i$, and display the $\pi$ value for $i = 10000, 20000, 30000, \dots, 100000$. What conclusion can you get?