这 能 A？！

#include<bits/stdc++.h>
using namespace std;
int main(){
    long long a,b,maxx=0;
    cin>>a>>b;
    for(long long i=a;i<=b;i++){
        maxx=max(maxx,(long long)__builtin_popcountll(i));
    }
    cout<<maxx;
}