How to get char from string by index?

Question

Lets say I have a string that consists of x unknown chars. How could I get char nr. 13 or char nr. x-14?

Answer 1

This should further clarify the points:

a = int(raw_input('Enter the index'))
str1 = 'Example'
leng = len(str1)
if (a < (len-1)) and (a > (-len)):
    print str1[a]
else:
    print('Index overflow')

Input 3 Output m

Input -3 Output p