a=0 #Напишите программу, которая обрабатывает файлы с результатами секвенирования.
c=0
g=0
t=0
u=0
b=0
try:
    f = open('3-in.txt', 'r')
except IOError as e:
    print('this file doesn`t exist')
else:
 l = [line.strip() for line in f]
 l.pop(0)
 l=list(''.join(l))
 for r in range(len(l)):
     if l[r]!='A' and l[r]!='a' and l[r]!='C' and l[r]!='c' and l[r]!='G' and l[r]!='g' and l[r]!='T' and l[r]!='t' and l[r]!='U' and l[r]!='u':
      print('this code includes external symbols')
      b+=1
      break
 if b==0:
  for i in range(len(l)):
   if l[i]=='A' or l[i]=='a':
     a +=1
   if l[i] == 'C' or l[i] == 'c':
     c += 1
   if l[i] == 'G' or l[i] == 'g':
     g += 1
   if l[i] == 'T' or l[i] == 't':
     t += 1
   if l[i] == 'U' or l[i] == 'u':
     u += 1
  if u!=0 and t!=0:
      print('this molecule can`t be sequenced')
  elif t!=0:
   print('DNA')
   print('A:',a)
   print('C:',c)
   print('G:',g)
   print('T:',t)
  else:
   print('RNA')
   print('A:', a)
   print('C:', c)
   print('G:', g)
   print('U:', u)