uses only simple math ( +, -, * , / ) to calculate pi
how it works: 1/1 + 1/3 - 1/5 + 1/7 - 1/9 + 1/11 - 1/13 + 1/15 - 1/17 + 1/19...... will give pi not that good takes like 24 million iterations to get to 3.1415926
