// Generic rot function
function rot( t, u, v ) {
 return String.fromCharCode( ( ( t - u + v ) % ( v * 2 ) ) + u );
}

// Rot13
function decodeForm(s){
	var b = [], c, i = s.length,
	a = 'a'.charCodeAt(), z = a + 26,
	A = 'A'.charCodeAt(), Z = A + 26;
	while(i--) {
		c = s.charCodeAt(i);
		if( c>=a && c<z ) { b[i] = rot(c, a, 13 ); }
		else if( c>=A && c<Z ) { b[i] = rot(c, A, 13 ); }
		else if (c == 94){ b[i] = '@'; }
		else { b[i] = s.charAt(i); }
	}
	return b.join( '' );
}