I REALLY NEED HELP WITH THIS CODE!!! plz help!

This is a problem from my computer science class...

An approximate value of pi can be calculated using the series given below:

pi = 4[ 1 - 1/3 + 1/5 - 1/7 + 1/9 ... + ((-1)^n) / (2n+1) ]

Write a C++ program to calculate the approximate value of pi using this series. The program takes an input "n" that determines the number of terms in the approximation of the value of pi and outputs the approximation. Include a loop that allows the user to repeat this calculation for new values of "n" until the user says she or he wants to end the program.

IF ANYONE COULD HELP ME WITH THE CODING, IT WOULD BE **GREATLY** APPRECIATED!!!!!