PIPIOJ 1436: PIPI's bit operation problem Ⅰ bit operation

http://pipioj.online/problem.php?id=1436

Idea: Combine $LandR\; are$ converted into binary representations, and enumerate from the high bit. Obviously, there are four cases for each bit (in fact, there are only three cases, because R>=L), when$R_i=1$ and$L_i=At\; 0$ , we can take all$R_j$Set to $0$，$L_j$Set to $1$ (j>i), this is the optimal solution.

#include<bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;

using ll=long long;

ll L,R;

int main()
{
    
    
    scanf("%lld%lld",&L,&R);
    ll ans=1ll<<60;
    while(ans)
    {
    
    
        if((R&ans)&&!(L&ans))
        {
    
    
            ans=(ans<<1)-1;
            break;
        }
        ans>>=1;
    }
    printf("%lld\n",ans);
    return 0;
}