#!/usr/bin/python

import sys
import random

def print_help():
  print "syntax is: randseq2.py {protX,prot,dna,dnan} length"

dna = dict({0:'A',1:'G',2:'C',3:'T'});
dnan = dict({0:'A',1:'G',2:'C',3:'T',4:'N'})
prot = dict({0:'G',1:'A',2:'L',3:'M',4:'F',5:'W',6:'K',7:'Q',8:'E',9:'S',10:'P',11:'V',12:'I',13:'C',14:'Y',15:'H',16:'R',17:'N',18:'D',19:'T'})
protX = dict({0:'G',1:'A',2:'L',3:'M',4:'F',5:'W',6:'K',7:'Q',8:'E',9:'S',10:'P',11:'V',12:'I',13:'C',14:'Y',15:'H',16:'R',17:'N',18:'D',19:'T',20:'X'})
if len(sys.argv)==1:
  print_help()
  raise SystemExit

if len(sys.argv)==2:
  if (sys.argv[1][len(sys.argv[1])-4:len(sys.argv[1])]=="help"):
    print_help()
    raise SystemExit

seq=""
if sys.argv[1]=="dna":
  ldict=dna;
if sys.argv[1]=="dnan":
  ldict=dnan;
if sys.argv[1]=="prot":
  ldict=prot;
if sys.argv[1]=="protX":
  ldict=protX;
for i in range (1,int(sys.argv[2])):
  seq += ldict[random.randint(0,len(ldict)-1)]

print seq