#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#include <utility>
#include <functional>
#include <time.h>
#include <stack>
#include <array>
#define popcount __builtin_popcount
using namespace std;
using ll=long long;
typedef pair<int, int> P;

int main()
{
    int x, k; cin>>x>>k;
    if(x==1){
        printf("%.7lf\n", 1.0-pow(0.5, k+1));
    }else{
        if(k==1) cout<<0.5<<endl;
        else if(k==2) printf("%.7lf\n", riemann_zeta(2)-1);
        else printf("%.7lf\n", (k-1)*riemann_zeta(k)-(k-2)*riemann_zeta(k-1));
    }
    return 0;
}