用除10取商记录位数，看可以除几次10，就是几位数 
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        scan.close();
        if(num < 0)
            System.out.println(num);
        else {
            int cnt = 0;
            while(num > 0){
                num = num / 10;
                cnt++;
            }
            System.out.println(cnt);
        }
    }