public class Solution {

    public int NumberOf1Between1AndN_Solution(int n) {

        int count=0;

        for(int i=1;i<=n;i++){

            count+=core(i);

        }

        return count;

    }

    private int core(int n){

        int num=0;

        while(n!=0){

            if(n%10==1){

                num++;

            }

            n/=10;

        }

        return num;

    }

}