#include<bits/stdc++.h>
using namespace std;
#define ll long long
bool check()
int main()
{
    ll l=0,r=1e9;//l 和 r是实际范围
    while(l<r)
    {
        ll mid=(l+r+1)>>1;
        if(check())
            l=mid;
        else
            r=mid-1;
    }
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
bool check(double x)
int main()
{
    double l=0,r=1e9;
    while(r-l>1e-3)
    {
        double mid=(l+r)/2;
        if(check(mid))
            l=mid;
        else
            r=mid;
    }
    return 0;
}