C#

public String getLetter(int? number)
{
    number -= 1;
    String letter = "";
    char[] lettersA = {
                         'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                         'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                         's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
                      };

    int size = number.Value % 26;
    int bigSize = number.Value % 676;
    int loop = (int)Math.Floor((decimal)(number.Value / 26));
    int bigLoop = (int)Math.Floor((decimal)(number.Value / 676));


    for (int i = 0; i < loop; i++)
    {
        letter += lettersA[i];
    }
    letter += lettersA[size];

    return letter;
}

<form id="form1" action="someurl.com" method="post">
<input type="hidden" name="abc" value="firstForm">
<input type="submit" value="firstForm" />                    
</form>
<form action="someurl.com" method="post">
<input type="hidden" name="abc" value="secondForm">
<input type="submit" value="secondForm" />                   
</form>