#include<stdio.h>
#include<math.h>
int main()
{
	int m,n;
	scanf("%d %d",&m,&n);
	int wei;
	int sign =0;
	for(int i =m;i<=n;i++)
	{
		int tmp = i;
		for(int j =0;;j++)
		{
			if(i/pow(10,j)==0)
			{
				wei = j;
				break;
			}
			else continue;
		}
		for(int k = wei-1;k>=0;k--)
		{
			int shu = pow(10,k);
			if(i/shu==2)
			{
				sign++;
				i = i%shu;
			}
			else
			{
				i = i%shu;
				continue;
			}
		}
		i = tmp;
	}
	printf("%d",sign);
	return 0;
}