#include<iostream>
#include<cmath>
#include<cstdio>
#include<algorithm>
using namespace std;
int main(){
	int m,n;
	cin >> m >> n;
	int res = 0;
	for(int i = m;i<=n;i++){
		int tmp = i;
		while(tmp){
			if(tmp%10 == 2){
				res++;
			}
			tmp/=10;
		}
	}
	cout << res;
	return 0;
}