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

高情商：递归 低情商：TLE

#include<iostream>
#include<cmath>
using namespace std;
double f(double x,double n)//递归函数
{
	if(n<=1)//递归边界
	{
		return sqrt(1+x);//结束递归
	}
	else
	{
		return sqrt(n+f(x,n-1));//递归
	}
}
int main()
{
	double a,b;
	cin>>a>>b;//输入
	printf("%.2lf",f(a,b));//保留两位(题目也没说)!!!
	return 0;//完结散花
}

#include<bits/stdc++.h>
using namespace std;

double f (double x,double n) {
	if (n<=1) {
		return sqrt(x+1);
	} else {
		return sqrt(n+f(x,n-1));
	}
}

int main () {
	double x,n; cin >> x >> n;
	printf("%.2lf",f(x,n));
	return 0;
}