#include <bits/stdc++.h>
using namespace std;

int main()
{
	int l, r, cnt = 0;
	cin >> l >> r;

	for (int i = l; i <= r; i++)
	{
		int t = i;
		while (t)
		{
			if (t % 10 == 2)
				cnt ++;
			t /= 10;
		}
	}
	cout << cnt << endl;

	return 0;
}