#include<stdio.h>
#include<iostream>
using namespace std;

int main(){
    int L=0,R=0;
    cin>>L>>R;
    int count = 0;
    for(int i = L; i<=R;i++){
        int t = i;
        while(t!=0){
            if((t%10) == 2){
                count++;
            }
            t /= 10;
        }
    }
    cout<<count;
}