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# the authors of referenced articles or incorporated external code:
# http://en.literateprograms.org/Pi_with_Machin's_formula_(Python)?action=history&offset=20071208004422
# 
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# Retrieved from: http://en.literateprograms.org/Pi_with_Machin's_formula_(Python)?oldid=11786

import sys

def arccot(x, unity):
    sum = xpower = unity // x
    n = 3
    sign = -1
    while 1:
        xpower = xpower // (x*x)
        term = xpower // n
        if not term:
            break
        sum += sign * term
        sign = -sign
        n += 2
    return sum

def pi(digits):
    unity = 10**(digits + 10)
    pi = 4 * (4*arccot(5, unity) - arccot(239, unity))
    return pi // 10**10


### MAIN ###

try:
	n = int (sys.argv[1])
except:
	print "Please give me the number of digits to calculate"
	sys.exit (1)

print "Calculating PI to %d digits." % n 
pi (n)
print