#include <bits/stdc++.h>
using namespace std;
int l,r,t=0,ans;
int main()
{
  cin>>l>>r;
  for (int i=l; i<=r; i++)
  {
    ans=i;
    while (ans!=0)
    {
      if (ans%10==2)t++;
      ans=ans/10;
    }
  }
  cout<<t;
  return 0;
}