s = 'hello'
puts s[0] # 104: the ASCII character code for the first character 'h'
puts s[s.length-1] # 111: the character code of the last character 'o'
puts s[-1] # 111: another way of accessing the last character
puts s[-2] # 108: the second-to-last character
puts s[-s.length] # 104: another way of accessing the first character
puts s[s.length] # nil: there is no character at that index