Write a program which counts and reports the number of each alphabetical letter. Ignore the case of characters.
A sentence in English is given in several lines.
Prints the number of alphabetical letters in the following format:
a : The number of 'a' b : The number of 'b' c : The number of 'c' . . z : The number of 'z'
This is a pen.
a : 1 b : 0 c : 0 d : 0 e : 1 f : 0 g : 0 h : 1 i : 2 j : 0 k : 0 l : 0 m : 0 n : 1 o : 0 p : 1 q : 0 r : 0 s : 2 t : 1 u : 0 v : 0 w : 0 x : 0 y : 0 z : 0