#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/rope>

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
 
typedef long long ll;
typedef long double ld;
typedef complex<ld> cd;

typedef pair<int, int> pi;
typedef pair<ll,ll> pl;
typedef pair<ld,ld> pd;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
typedef vector<cd> vcd;

template <class T> using Tree = tree<T, null_type, less<T>, rb_tree_tag,tree_order_statistics_node_update>;

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i,a,b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i,a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto& a : x)

#define mp make_pair
#define pb push_back
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound

#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rsz resize

const int MOD = 1000000007; // 998244353
const ll INF = 1e18;
const int MX = 200005;
const ld PI = 4*atan((ld)1);

template<class T> void ckmin(T &a, T b) { a = min(a, b); }
template<class T> void ckmax(T &a, T b) { a = max(a, b); }

namespace input {
    template<class T> void re(complex<T>& x);
    template<class T1, class T2> void re(pair<T1,T2>& p);
    template<class T> void re(vector<T>& a);
    template<class T, size_t SZ> void re(array<T,SZ>& a);

    template<class T> void re(T& x) { cin >> x; }
    void re(double& x) { string t; re(t); x = stod(t); }
    void re(ld& x) { string t; re(t); x = stold(t); }
    template<class Arg, class... Args> void re(Arg& first, Args&... rest) { 
        re(first); re(rest...); 
    }

    template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = cd(a,b); }
    template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
    template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
    template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}

using namespace input;

namespace output {
    template<class T1, class T2> void pr(const pair<T1,T2>& x);
    template<class T, size_t SZ> void pr(const array<T,SZ>& x);
    template<class T> void pr(const vector<T>& x);
    template<class T> void pr(const set<T>& x);
    template<class T1, class T2> void pr(const map<T1,T2>& x);

    template<class T> void pr(const T& x) { cout << x; }
    template<class Arg, class... Args> void pr(const Arg& first, const Args&... rest) { 
        pr(first); pr(rest...); 
    }

    template<class T1, class T2> void pr(const pair<T1,T2>& x) { 
        pr("{",x.f,", ",x.s,"}"); 
    }
    template<class T> void prContain(const T& x) {
        pr("{");
        bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; // const needed for vector<bool>
        pr("}");
    }
    template<class T, size_t SZ> void pr(const array<T,SZ>& x) { prContain(x); }
    template<class T> void pr(const vector<T>& x) { prContain(x); }
    template<class T> void pr(const set<T>& x) { prContain(x); }
    template<class T1, class T2> void pr(const map<T1,T2>& x) { prContain(x); }
    
    void ps() { pr("\n"); }
    template<class Arg> void ps(const Arg& first) { 
        pr(first); ps(); // no space at end of line
    }
    template<class Arg, class... Args> void ps(const Arg& first, const Args&... rest) { 
        pr(first," "); ps(rest...); // print w/ spaces
    }
}

using namespace output;

namespace io {
    void setIn(string s) { freopen(s.c_str(),"r",stdin); }
    void setOut(string s) { freopen(s.c_str(),"w",stdout); }
    void setIO(string s = "") {
        ios_base::sync_with_stdio(0); cin.tie(0); // fast I/O
        if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
    }
}

using namespace io;

template<class T> T invGeneral(T a, T b) {
    a %= b; if (a == 0) return b == 1 ? 0 : -1;
    T x = invGeneral(b,a); 
    return x == -1 ? -1 : ((1-(ll)b*x)/a+b)%b;
}

template<class T> struct modular {
    T val; 
    explicit operator T() const { return val; }
    modular() { val = 0; }
    template<class U> modular(const U& v) {
        val = (-MOD <= v && v <= MOD) ? v : v % MOD;
        if (val < 0) val += MOD;
    }
    friend ostream& operator<<(ostream& os, const modular& a) { return os << a.val; }
    friend bool operator==(const modular& a, const modular& b) { return a.val == b.val; }
    friend bool operator!=(const modular& a, const modular& b) { return !(a == b); }

    modular operator-() const { return modular(-val); }
    modular& operator+=(const modular& m) { if ((val += m.val) >= MOD) val -= MOD; return *this; }
    modular& operator-=(const modular& m) { if ((val -= m.val) < 0) val += MOD; return *this; }
    modular& operator*=(const modular& m) { val = (ll)val*m.val%MOD; return *this; }
    friend modular exp(modular a, ll p) {
        modular ans = 1; for (; p; p /= 2, a *= a) if (p&1) ans *= a;
        return ans;
    }
    friend modular inv(const modular& a) { 
        auto i = invGeneral(a.val,MOD); assert(i != -1);
        return i;
    } // equivalent to return exp(b,MOD-2) if MOD is prime
    modular& operator/=(const modular& m) { return (*this) *= inv(m); }
    
    friend modular operator+(modular a, const modular& b) { return a += b; }
    friend modular operator-(modular a, const modular& b) { return a -= b; }
    friend modular operator*(modular a, const modular& b) { return a *= b; }
    
    friend modular operator/(modular a, const modular& b) { return a /= b; }
};

typedef modular<int> mi;
typedef pair<mi,mi> pmi;
typedef vector<mi> vmi;
typedef vector<pmi> vpmi;

namespace point {
    typedef pd P;
    typedef vector<P> vP;

    P dir(ld ang) {
        cd c = exp(ang*cd(0,1));
        return P(c.real(),c.imag());
    }
    
    ld norm(P x) { return x.f*x.f+x.s*x.s; }
    ld abs(P x) { return sqrt(norm(x)); }
    ld angle(P x) { return atan2(x.s,x.f); }
    P conj(P x) { return P(x.f,-x.s); }
    
    P operator+(const P& l, const P& r) { return P(l.f+r.f,l.s+r.s); }
    P operator-(const P& l, const P& r) { return P(l.f-r.f,l.s-r.s); }
    P operator*(const P& l, const ld& r) { return P(l.f*r,l.s*r); }
    P operator*(const ld& l, const P& r) { return r*l; }
    P operator/(const P& l, const ld& r) { return P(l.f/r,l.s/r); }
    P operator*(const P& l, const P& r) { return P(l.f*r.f-l.s*r.s,l.s*r.f+l.f*r.s); }
    P operator/(const P& l, const P& r) { return l*conj(r)/norm(r); }
    
    P& operator+=(P& l, const P& r) { return l = l+r; }
    P& operator-=(P& l, const P& r) { return l = l-r; }
    P& operator*=(P& l, const ld& r) { return l = l*r; }
    P& operator/=(P& l, const ld& r) { return l = l/r; }
    P& operator*=(P& l, const P& r) { return l = l*r; }
    P& operator/=(P& l, const P& r) { return l = l/r; }
    
    P unit(P x) { return x/abs(x); }
    
    ld dot(P a, P b) { return (conj(a)*b).f; }
    ld cross(P a, P b) { return (conj(a)*b).s; }
    ld cross(P p, P a, P b) { return cross(a-p,b-p); }
    ld dist(P p, P a, P b) { return std::abs(cross(p,a,b))/abs(a-b); }
    
    P rotate(P a, ld b) { return a*P(cos(b),sin(b)); }
    P reflect(P p, P a, P b) { return a+conj((p-a)/(b-a))*(b-a); }
    P foot(P p, P a, P b) { return (p+reflect(p,a,b))/(ld)2; }
    P extension(P a, P b, P c, P d) {
        ld x = cross(a,b,c), y = cross(a,b,d);
        return (d*x-c*y)/(x-y);
    }
    // computes the intersection of line segments AB, CD
    // verification: https://open.kattis.com/problems/segmentintersection
    vP segIntersect(P a, P b, P c, P d) {
        if (a > b) swap(a,b);
        if (c > d) swap(c,d);
    
        auto a1 = cross(a,b,c), a2 = cross(a,b,d);
        if (a1 > a2) swap(a1,a2);
        if (!(a1 <= 0 && a2 >= 0)) return {};
    
        if (a1 == 0 && a2 == 0) {
            if (cross(a,c,d) != 0) return {};
            auto x1 = max(a,c), x2 = min(b,d);
            if (x1 > x2) return {};
            if (x1 == x2) return {x1};
            return {x1,x2};
        }
        
        auto z = extension(a,b,c,d);
        if (a <= z && z <= b) return {z};
        return {};
    }
    
    // sorts points according to atan2
    // verification: ?
    template<class T> int half(pair<T,T> x) { return mp(x.s,x.f) > mp((T)0,(T)0); }
    bool cmp(P a, P b) { 
        int A = half(a), B = half(b);
        if (A != B) return A < B;
        return cross(a,b) > 0;
    }
    
    // computes the center of mass of a polygon with constant mass per unit area
    // verification: kattis polygonarea, VT HSPC 2018 Holiday Stars
    ld area(const vP& v) {
        ld area = 0;
        F0R(i,sz(v)) {
            int j = (i+1)%sz(v); ld a = cross(v[i],v[j]);
            area += a;
        }
        return std::abs(area)/2;
    }
    P centroid(const vP& v) { 
        P cen(0,0); ld area = 0; // 2*signed area
        F0R(i,sz(v)) {
            int j = (i+1)%sz(v); ld a = cross(v[i],v[j]);
            cen += a*(v[i]+v[j]); area += a;
        }
        return cen/area/(ld)3;
    }
    
    // tests whether a point is inside, on, or outside the perimeter of any polygon
    // verification: https://open.kattis.com/problems/pointinpolygon
    string inPoly(const vP& p, P z) {
        int n = sz(p), ans = 0;
        F0R(i,n) {
            P x = p[i], y = p[(i+1)%n];
            if (cross(x,y,z) == 0 && min(x,y) <= z && z <= max(x,y)) return "on";
            if (x.s > y.s) swap(x,y);
            if (x.s <= z.s && y.s > z.s && cross(z,x,y) > 0) ans ^= 1;
        }
        return ans ? "in" : "out";
    }

    pair<P,double> ccCenter(P a, P b, P c) {
        b -= a; c -= a;
        P res = b*c*(conj(c)-conj(b))/(b*conj(c)-conj(b)*c);
        return {a+res,abs(res)};
    }
     
    pair<P, double> mec(vP ps) { // minimum enclosing circle, ex. USACO Camp 2019 Contest 2 #4
        shuffle(all(ps), mt19937(time(0)));
        P o = ps[0]; double r = 0, EPS = 1 + 1e-8;
        F0R(i,sz(ps)) if (abs(o-ps[i]) > r*EPS) {
            o = ps[i], r = 0;
            F0R(j,i) if (abs(o-ps[j]) > r*EPS) {
                o = (ps[i]+ps[j])/2, r = abs(o-ps[i]);
                F0R(k,j) if (abs(o-ps[k]) > r*EPS) 
                    tie(o,r) = ccCenter(ps[i],ps[j],ps[k]);
            }
        }
        return {o,r};
    }
};

using namespace point;

ll N,K;
P p[MX];

double area(int a, int b, int c) {
    return abs(cross(p[0],p[a],p[a+b]))/2;
}

ll get(ld mid) {
    ll ans = 0;
    FOR(i,1,N-1) {
        int mn = 0, mx = (N-i)/2;
        while (mn < mx) {
            int m = (mn+mx+1)/2;
            if (area(i,m,N-i-m) <= mid) mn = m;
            else mx = m-1;
        }
        ans += 2*mx;
        if (2*mx == N-i) ans --;
    }
    return ans;
}

int main() {
    setIO(); re(N,K);
    F0R(i,N) p[i] = dir(2*PI*i/N);
    double lo = 0, hi = 2;
    F0R(i,40) {
        ld mid = (lo+hi)/2;
        if (N*get(mid) >= 3*K) hi = mid;
        else lo = mid;
    }
    cout << fixed << setprecision(11) << (lo+hi)/2;
}


/* stuff you should look for
    * int overflow, array bounds
    * special cases (n=1?), set tle
    * do smth instead of nothing and stay organized
*/

Measured memory_bytes: 2176