# -*- coding: utf-8 -*-
"""
Created on Thu Mar 29 16:18:18 2018
@author: stkarlos
"""
a = 'ARTERTaabntrur'
#metrame sinoliko plithos a and A
print a.count('a') + a.count('A') #combinatory
print (a.upper()).count('A') #safe way
print a.lower().count('a') #directly