#include <bits/stdc++.h>
using namespace std;
double f(double n,double x){
	if(n==1)return sqrt(1+x);
	else return sqrt(n+f(n-1,x));
} 
int main(){
	double x,n;
	cin>>x>>n;
	printf("%.2f",f(n,x));
	return 0;
}