#include <iostream>
using namespace std;

int main() {
    int L, R, count = 0;
    cin >> L >> R;
    
    for (int i = L; i <= R; ++i) {   // 遍历区间内每个数
        int num = i;
        while (num > 0) {            // 逐位检查
            if (num % 10 == 2) count++;
            num /= 10;
        }
    }
    
    cout << count << endl;
    return 0;
}