#include <iostream>
using namespace std;
int cal(int x)
{
	int t(0);
	while(x)
	{
		if(x%10==2)
			t++;
		x/=10;
	}
	return t;
}
int main()
{
	int l,r,ans(0);
	cin>>l>>r;
	for(int i=l;i<=r;i++)
		ans+=cal(i);
	cout<<ans<<endl;
	return 0;
}
/**************************************************************
	Problem: 2292
	User: admin
	Language: C++
	Result: Accepted
	Time:47 ms
	Memory:2072 kb
****************************************************************/