#pragma GCC Optimize("Ofast")
#include<bits/stdc++.h>
#define endl '\n'
using namespace std;

int n,t;

int main()
{
//ios::sync_with_stdio(false);
//cin.tie(NULL);
//cout.tie(NULL);
freopen("dice.in","r",stdin);
freopen("dice.out","w",stdout);

cin>>n>>t;
long double a=0;
for(int i=1;i<=t;i++)
{
    int b=floor(a);
    a=(a*b+(b+1+n)*(n-b)/2)/n;
}
cout<<fixed<<setprecision(10)<<a<<endl;
return 0;
}