三分

题目

code

#include<bits/stdc++.h>
#define ld double
#define ll long long
using namespace std;
ld a,b;
ll l=1,r=1e18;
ld k;
ld d(ll mid){
	return b*(mid-1)+a/sqrt((ld)mid);
}
int main(){
	cin>>a>>b;
	while(l+2<r){
		ll m1=l+(r-l)/3,m2=r-(r-l)/3;
		if(d(m1)>d(m2)) l=m1;
		else r=m2;
	}
	while(d(r-1)<d(r)) r--;
	printf("%.10lf",d(r));
}