#include <iostream>
using namespace std;
typedef long long ll;
int cal(int t){
    int cnt = 0;
    while(t){
        if(t % 10 == 2) cnt ++ ;
        t /= 10;
    }
    return cnt;
}
int main(){
    int l, r;   cin >> l >> r;
    ll res = 0;
    for(int i = l; i <= r; i ++ )   res += cal(i);
    cout << res << endl;
    return 0;
}