#include <iostream>
using namespace std;

int main() {
    int l,r;
    cin>>l>>r;
    int ret=0;
    for(int i=l;i<=r;++i){
        int tmp=i;
        while(tmp){
            if(tmp%10==2) ret++;
            tmp/=10;
        }
    }
    cout << ret << endl;
    return 0;
}