#include <bits/stdc++.h>
using namespace std;
int main()
{
    int l, r, ans;
    cin >> l >> r;
    ans = 0;
    for (int i = l; i <= r; i++)
    {
        int now = 0; //计算 i 里有几个 2
        for (int j = i; j > 0; j /= 10)
            if (j % 10 == 2)
                now++;
        ans += now;
    }
    cout << ans;
    return 0;
}