lol

    public void printFactorial(Object o) {
        o = String.valueOf(o);
        if(o.getClass().getName().toLowerCase().equals("java.lang.String".toLowerCase())) {
            boolean isinterger = false;
            if(((String) o).charAt(0) == "-".charAt(0)) {
                System.out.println("[Err] Negative value");
                return;
            }
            for(int i=0;i < ((String) o).length();i++) {
                if(!((((String) o).charAt(i) >= '0') && (((String) o).charAt(i)) < '9'))
                    break;
                if(i==((String) o).length()-1) isinterger = true;
            }
            if(isinterger == true) {
                int num = 0, power;
                String number = (String)o;
                for(int i=0;i<number.length();i++) {
                    power = 1;
                    for(int ii=0;ii < i;ii++) {
                        power = power * 10;
                    }
                    num += ((number.charAt(number.length()-1-i) - "0".charAt(0)) * power);
                }
                num = num + 1;
                int factorial = 1;
                while((num = num - 1) > "".length()) {
                    factorial = num * factorial;
                }
                System.out.println(factorial);
            }
        }
    }