>>22-23
せめてニュートン法くらい使えよw

>>> def r2(m):
...  p0 = 2*10**m
...  p = p0
...  while(not ((p0-3)*10**m <= p*p and p*p <= (p0+3)*10**m)):
...   p = (p*p + p0*10**m) / (2*p)
...  print p
...
>>> r2(4)
14142
>>> r2(10)
14142135623
>>> r2(100)
14142135623730950488016887242096980785696718753769480731766797379907324784621070388503875343276415727