import cmath as cm
import numpy as np
def src(a,b,c):
 dt=cm.sqrt(b**2-4.*a*c)
 x1=(-b+dt)/(2.*a)
 x2=(-b-dt)/(2.*a)
 return x1,x2
def fact(n):
 if n <0:
  return "Error: negative number"
 if n == 0:
  return 1
 fac=1
 nn=np.linspace(1,n,num=n)
 print nn
 for i in nn:
  fac=fac*i
  print i
 return fac
def sum(a):
 n=len(a)
 sum=0.
 print a
 for i in a:
  sum=sum+i
 return sum,sum/n