#include<stdio.h>

int main()

{

    int count=0;

    int n, k,i;

    scanf("%d %d", &n, &k);

    for (i = n; i <= k; i++)

    {

        int j=i;

        while(j>0)

        {

            if (j % 10 == 2) //取余

            {

                count++;

            }

            j = j / 10;     //移动到前一位

        }

    }

    printf("%d\n", count);

    return 0;

}