#include<iostream>
#include<algorithm>

using namespace std;
int cal (int x) {
    int cnt = 0;
    while (x) {
        cnt += (x % 10 == 2);
        x /= 10;
    }
    return cnt;
}
int main () {
    int L,R;
    cin >> L >> R;
    int ans = 0;
    for (int i = L;i <= R;i++) {
        ans += cal(i); 
    }
    cout << ans << endl;
}