public class EncryptString
{
	
	public  string Encrypt(string strValue)
	{
		return genNewString(strValue);
		
	}
	private string genNewString(string strValue)
	{
		int i,j,k;
		string strNewStringValue="";
		char [] chrValue = strValue.ToCharArray();

		for ( i=0; i<=chrValue.Length-1; i++)
		{
			// take the next character in the string
			j = (int)chrValue[i];

			// find out the character code
			k = (int)j;

			if (k >= 97 && k <= 109)
			{
				// a ... m inclusive become n ... z
				k = k + 13;
			}
			else if( k >= 110 && k <= 122 )
			{
				// n ... z inclusive become a ... m
				k = k - 13;
			}
			else if (k >= 65 && k <= 77)
			{
				// A ... m inclusive become n ... z
				k = k + 13 ;
			}
			else if( k >= 78 && k <= 90 )
			{
				// N ... Z inclusive become A ... M
				k = k - 13;
			}
				
			//add the current character to the string returned by the function
			strNewStringValue = strNewStringValue +(char)k;
		}

		return strNewStringValue ;				
	}
}