text: #include <bits/stdc++.h>
  using namespace std;
   
  typedef long long ll;
  typedef long double ld;
  typedef double db; 
  typedef string str; 
  
  typedef pair<int,int> pi;
  typedef pair<ll,ll> pl; 
  typedef pair<db,db> pd; 
  
  typedef vector<int> vi; 
  typedef vector<ll> vl; 
  typedef vector<db> vd; 
  typedef vector<str> vs; 
  typedef vector<pi> vpi;
  typedef vector<pl> vpl; 
  typedef vector<pd> vpd; 
  
  #define mp make_pair
  #define f first
  #define s second
  #define sz(x) (int)(x).size()
  #define all(x) begin(x), end(x)
  #define rall(x) (x).rbegin(), (x).rend() 
  #define rsz resize
  #define ins insert 
  #define ft front() 
  #define bk back()
  #define pf push_front 
  #define pb push_back
  #define eb emplace_back 
  #define lb lower_bound 
  #define ub upper_bound 
  
  #define FOR(i,a,b) for (int i = (a); i < (b); ++i)
  #define F0R(i,a) FOR(i,0,a)
  #define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
  #define R0F(i,a) ROF(i,0,a)
  #define trav(a,x) for (auto& a: x)
  
  const int MOD = 1e9+7; // 998244353;
  const int MX = 2e5+5; 
  const ll INF = 1e18; 
  const ld PI = acos((ld)-1);
  const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; 
  mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 
  
  template<class T> bool ckmin(T& a, const T& b) { 
  	return b < a ? a = b, 1 : 0; }
  template<class T> bool ckmax(T& a, const T& b) { 
  	return a < b ? a = b, 1 : 0; } 
  constexpr int pct(int x) { return __builtin_popcount(x); } 
  constexpr int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x)) 
  ll cdiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
  ll fdiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down
  ll half(ll x) { return fdiv(x,2); }
  
  template<class T, class U> T fstTrue(T lo, T hi, U f) {
  	hi ++; assert(lo <= hi); // assuming f is increasing
  	while (lo < hi) { // find first index such that f is true 
  		T mid = half(lo+hi);
  		f(mid) ? hi = mid : lo = mid+1; 
  	} 
  	return lo;
  }
  template<class T, class U> T lstTrue(T lo, T hi, U f) {
  	lo --; assert(lo <= hi); // assuming f is decreasing
  	while (lo < hi) { // find first index such that f is true 
  		T mid = half(lo+hi+1);
  		f(mid) ? lo = mid : hi = mid-1;
  	} 
  	return lo;
  }
  template<class T> void remDup(vector<T>& v) { 
  	sort(all(v)); v.erase(unique(all(v)),end(v)); }
  
  // INPUT
  template<class A> void re(complex<A>& c);
  template<class A, class B> void re(pair<A,B>& p);
  template<class A> void re(vector<A>& v);
  template<class A, size_t SZ> void re(array<A,SZ>& a);
  
  template<class T> void re(T& x) { cin >> x; }
  void re(db& d) { str t; re(t); d = stod(t); }
  void re(ld& d) { str t; re(t); d = stold(t); }
  template<class H, class... T> void re(H& h, T&... t) { re(h); re(t...); }
  
  template<class A> void re(complex<A>& c) { A a,b; re(a,b); c = {a,b}; }
  template<class A, class B> void re(pair<A,B>& p) { re(p.f,p.s); }
  template<class A> void re(vector<A>& x) { trav(a,x) re(a); }
  template<class A, size_t SZ> void re(array<A,SZ>& x) { trav(a,x) re(a); }
  
  // TO_STRING
  #define ts to_string
  str ts(char c) { return str(1,c); }
  str ts(const char* s) { return (str)s; }
  str ts(str s) { return s; }
  str ts(bool b) { 
  	#ifdef LOCAL
  		return b ? "true" : "false"; 
  	#else 
  		return ts((int)b);
  	#endif
  }
  template<class A> str ts(complex<A> c) { 
  	stringstream ss; ss << c; return ss.str(); }
  str ts(vector<bool> v) {
  	str res = "{"; F0R(i,sz(v)) res += char('0'+v[i]);
  	res += "}"; return res; }
  template<size_t SZ> str ts(bitset<SZ> b) {
  	str res = ""; F0R(i,SZ) res += char('0'+b[i]);
  	return res; }
  template<class A, class B> str ts(pair<A,B> p);
  template<class T> str ts(T v) { // containers with begin(), end()
  	#ifdef LOCAL
  		bool fst = 1; str res = "{";
  		for (const auto& x: v) {
  			if (!fst) res += ", ";
  			fst = 0; res += ts(x);
  		}
  		res += "}"; return res;
  	#else
  		bool fst = 1; str res = "";
  		for (const auto& x: v) {
  			if (!fst) res += " ";
  			fst = 0; res += ts(x);
  		}
  		return res;
  
  	#endif
  }
  template<class A, class B> str ts(pair<A,B> p) {
  	#ifdef LOCAL
  		return "("+ts(p.f)+", "+ts(p.s)+")"; 
  	#else
  		return ts(p.f)+" "+ts(p.s);
  	#endif
  }
  
  // OUTPUT
  template<class A> void pr(A x) { cout << ts(x); }
  template<class H, class... T> void pr(const H& h, const T&... t) { 
  	pr(h); pr(t...); }
  void ps() { pr("\n"); } // print w/ spaces
  template<class H, class... T> void ps(const H& h, const T&... t) { 
  	pr(h); if (sizeof...(t)) pr(" "); ps(t...); }
  
  // DEBUG
  void DBG() { cerr << "]" << endl; }
  template<class H, class... T> void DBG(H h, T... t) {
  	cerr << ts(h); if (sizeof...(t)) cerr << ", ";
  	DBG(t...); }
  #ifdef LOCAL // compile with -DLOCAL, chk -> fake assert
  	#define dbg(...) cerr << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
  	#define chk(...) if (!(__VA_ARGS__)) cerr << "Line(" << __LINE__ << ") -> function(" \
  		 << __FUNCTION__  << ") -> CHK FAILED: (" << #__VA_ARGS__ << ")" << "\n", exit(0);
  #else
  	#define dbg(...) 0
  	#define chk(...) 0
  #endif
  
  // FILE I/O
  void setIn(str s) { freopen(s.c_str(),"r",stdin); }
  void setOut(str s) { freopen(s.c_str(),"w",stdout); }
  void unsyncIO() { ios_base::sync_with_stdio(0); cin.tie(0); }
  void setIO(str s = "") {
  	unsyncIO();
  	// cin.exceptions(cin.failbit); 
  	// throws exception when do smth illegal
  	// ex. try to read letter into int
  	if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
  }
  
  const int a = 2019201997-2019201913;
  const int b = 2019201997-2019201949;
  
  int N,K;
  
  const int WUT = ((1<<16)-1);
  
  pi rhsh(int x) {
  	return {x>>16,x&WUT};
  }
  
  int wei(int x) {
  	return (x>>16)*a+(x&WUT)*b;
  }
  
  
  int hsh(int a, int b) { return (a<<16)+b; }
  
  /**
   * Description: Disjoint Set Union with path compression
   	* and union by size. Add edges and test connectivity. 
   	* Use for Kruskal's or Boruvka's minimum spanning tree.
   * Time: O(\alpha(N))
   * Source: CSAcademy, KACTL
   * Verification: *
   */
  
  struct DSU {
  	vi e; void init(int N) { e = vi(N,-1); }
  	int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); } 
  	bool sameSet(int a, int b) { return get(a) == get(b); }
  	int size(int x) { return -e[get(x)]; }
  	bool unite(int x, int y) { // union by size
  		x = get(x), y = get(y); if (x == y) return 0;
  		if (e[x] > e[y]) swap(x,y);
  		e[x] += e[y]; e[y] = x; return 1;
  	}
  };
  
  /**template<class T> T kruskal(int N, vector<pair<T,pi>> ed) {
  	sort(all(ed));
  	T ans = 0; DSU D; D.init(N); // edges that unite are in MST
  	trav(a,ed) if (D.unite(a.s.f,a.s.s)) ans += a.f; 
  	return ans;
  }*/
  
  const int SZ = 28121250;
  int ed[SZ], res[SZ];
  DSU D;
  
  template<class F> void bucket(int a[], int b[], const F& f) {
  	vi cnt(1<<16);
  	F0R(i,N*(N-1)/2) cnt[f(a[i])] ++;
  	int sum = 0;
  	R0F(i,1<<16) {
  		swap(sum,cnt[i]);
  		sum += cnt[i];
  	}
  	F0R(i,N*(N-1)/2) b[cnt[f(a[i])]++] = a[i];
  }
  
  int main() {
  	setIO("walk"); 
  	clock_t beg = clock();
  	re(N,K); D.init(N+1);
  	int cnt = 0; FOR(i,1,N+1) FOR(j,i+1,N+1) ed[cnt++] = hsh(i,j);
  	dbg((db)(clock()-beg)/CLOCKS_PER_SEC);
  	bucket(ed,res,[](int x) { return wei(x)&WUT; });
  	dbg((db)(clock()-beg)/CLOCKS_PER_SEC);
  	bucket(res,ed,[](int x) { return wei(x)>>16; });
  	dbg((db)(clock()-beg)/CLOCKS_PER_SEC);
  	vi ans;
  	F0R(i,N*(N-1)/2) {
  		int t = ed[i];
  		pi p = rhsh(t);
  		if (D.unite(p.f,p.s)) ans.pb(2019201997-wei(t));
  	}
  	ps(ans[N-K]);
  	dbg((db)(clock()-beg)/CLOCKS_PER_SEC);
  	// you should actually read the stuff at the bottom
  }
  
  /* stuff you should look for
  	* int overflow, array bounds
  	* special cases (n=1?)
  	* do smth instead of nothing and stay organized
  	* WRITE STUFF DOWN
  */
  
  