Problem:
Toggling Cases

Write a program which converts uppercase/lowercase letters to lowercase/uppercase for a given string.

Input

A string is given in a line.

Output

Print the converted string in a line. Note that you do not need to convert any characters other than alphabetical letters.

Constraints

The length of the input string < 1200

Sample Input

fAIR, LATER, OCCASIONALLY CLOUDY.

Sample Output

Fair, later, occasionally cloudy.

Solution in C# (judge verdict: Runtime Error)

using System;

class Program
{
    static void Main()
    {
            string inp = Console.ReadLine();
            int i = 0;bool end = true;
            while (end == true)
            {
                if (inp[i] == '.')
                {
                    Console.Write(".");
                    break;
                }
                if (char.IsUpper(inp,i))
                {
                    Console.Write(char.ToLower(inp[i]));
                }
                else if (char.IsLower(inp,i))
                {
                    Console.Write(char.ToUpper(inp[i]));
                }
                else
                {
                   Console.Write(inp[i]);

                }
                i++;
            }
            Console.Write("\n");
    }
}