代码献上

#include<bits/stdc++.h>
#define int long long
using namespace std;

int nbegin,nend,ans;

int check(int num,int temp)
{
    if(num<=0) return temp;
    if(num%10==2) check(num/10,temp++);
    check(num/10,temp);
}

signed main()
{
    cin>>nbegin>>nend;
    for(int times=nbegin;times<=nend;times++) ans+=check(times,0);
    cout<<ans;
    cout<<sizeof(nbegin)+sizeof(nend)+sizeof(ans);
}