String.prototype.getInt = function(i, minlength, maxlength) {
	for(var x = maxlength ; x >= minlength ; x--) {
		var token=this.substring(i, i+x);
		if(token.length < minlength)
			return null;
		if(token.isInteger())
			return token;
	}
	return null;
}

String.prototype.isInteger = function() {
	var digits="1234567890";
	for(var i = 0 ; i < this.length ; i++) {
		if(digits.indexOf(this.charAt(i)) == -1) return false;
	}
	return true;
}