#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main(){
    double x;
    int n;cin >>x>>n;
    double result=x;
    for (int i=1;i<=n;i++) 
    {
        result=i+result;
        result=sqrt(result);
    }
    cout<<fixed<<setprecision(2)<<result<<endl;
    return 0;
}