Problem:
Counting Characters

Write a program which counts and reports the number of each alphabetical letter. Ignore the case of characters.

Input

A sentence in English is given in several lines.

Output

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'

Constraints

The number of characters in the sentence < 1200

Sample Input

This is a pen.

Sample Output

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

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{

    static int CountLetter(char s, List<char> letter2)
    {
        int count = 0;

        for (int i = 0; i < letter2.Count; i++)
        {
            if (letter2[i] == s || letter2[i] == Char.ToUpper(s))
            {
                count++;
            }
        }
        
        return count;
    }


    static void Main(string[] args)
    {
        string str = "abcdefghijklmnopqrstuvwxyz";
        var letter = new List<char>();
       
        do
        {           
            string input = Console.ReadLine();
            if (string.IsNullOrEmpty(input))
            {
                break;
            }

            foreach(var s in input)
            {
                letter.Add(s);
            }         
            
        } while (true);

        int count = 0;
      
        foreach (var s in str)
        {
            count = CountLetter(s, letter);
            Console.WriteLine($"{s} : {count}");
        }                                
    }
}