/* #pragma region GNUC //https://yukicoder.me/wiki/auto_vectorization #ifdef __GNUC__ #pragma GCC optimize ("O3") #pragma GCC target ("avx") #endif #pragma endregion */ #define _USE_MATH_DEFINES #pragma region include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //#include #include #pragma endregion //#include ///////// #define REP(i, x, n) for(int i = x; i < n; ++i) #define rep(i,n) REP(i,0,n) ///////// #pragma region typedef typedef long long LL; typedef long double LD; typedef unsigned long long ULL; #pragma endregion //typedef ////定数 const int INF = (int)1e9; const LL MOD = (LL)1e9+7; const LL LINF = (LL)1e18; const double PI = acos(-1.0); const double EPS = 1e-9; ///////// using namespace::std; ///////// #pragma region Math #pragma region template inline T gcd(T a, T b){return b ? gcd(b, a % b) : a;} #pragma endregion // 最大公約数 gcd #pragma region template inline T lcm(T a, T b){return a / gcd(a, b) * b;} #pragma endregion // 最小公倍数 lcm #pragma region LL powMod(LL num,LL n,LL mod=(LL)MOD){ if( n == 0 ){ return (LL)1; } LL mul = num; LL ans = (LL)1; while(n){ if( n&1 ){ ans = (ans*mul)%mod; } mul = (mul*mul)%mod; n >>= 1; } return ans; } #pragma endregion //繰り返し二乗法 powMod #pragma region template vector getDivisor(T n){ vector v; for(int i=1;i*i<=n;++i){ if( n%i == 0 ){ v.push_back(i); if( i != n/i ){//平方数で重複して数えないように v.push_back(n/i); } } } sort(v.begin(), v.end()); return v; } #pragma endregion //約数列挙 getDivisor(n):O(√n) #pragma endregion //math //Utility:便利な奴 #pragma region template void UNIQUE(vector& vec){ sort(vec.begin(),vec.end()); vec.erase(unique(vec.begin(),vec.end()),vec.end() ); } #pragma endregion // sort erase unique //////////////////////////////// #pragma region long long bitcount64(long long bits) { bits = (bits & 0x5555555555555555) + (bits >> 1 & 0x5555555555555555); bits = (bits & 0x3333333333333333) + (bits >> 2 & 0x3333333333333333); bits = (bits & 0x0f0f0f0f0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f0f0f0f0f); bits = (bits & 0x00ff00ff00ff00ff) + (bits >> 8 & 0x00ff00ff00ff00ff); bits = (bits & 0x0000ffff0000ffff) + (bits >>16 & 0x0000ffff0000ffff); return (bits & 0x00000000ffffffff) + (bits >>32 & 0x00000000ffffffff); } #pragma endregion //その他 //////////////////////////////// struct edge_base{int to;LL cost;}; edge_base make_edge_base(int to,LL cost){ edge_base ret = {to,cost}; return ret; } #pragma region GRL #pragma region //グラフ template void dijkstra(int root,int V,vector& dist, vector< vector > G ){ priority_queue,vector >,greater > > que; dist.assign(V,LINF); dist[root] = 0; que.push(pair(0,root));//距離、頂点番号 while( !que.empty() ){ pair p = que.top();que.pop(); int v = p.second; if( dist[v] < p.first ) continue; for(int i=0;i < (int)G[v].size();++i){ EDGE e = G[v][i]; if( dist[e.to] > dist[v] + e.cost ){ dist[e.to] = dist[v] + e.cost; que.push(pair(dist[e.to],e.to)); } } } } #pragma endregion //ダイクストラ法:O(|E|log|V|) #pragma region //グラフ void warshall_floyd(vector >& dist,int V,const LL INF=LINF){ for(int k=0;k= INF ) continue; for(int j=0;j= INF )continue; dist[i][j] = min(dist[i][j],dist[i][k]+dist[k][j]); } } } } #pragma endregion //ワーシャルフロイド:O(|V|**3) #pragma region namespace FLOW{ //vector< vector > G; struct edge_flow : public edge_base{ int cap; int rev; }; edge_flow make_edge_flow(int to,int cap,int rev,LL cost=1){ edge_flow ret; ret.to = to; ret.cost = cost; ret.cap = cap; ret.rev = rev; return ret; } class Graph{ public: int V; vector< vector > G; vector< LL > dist; vector< int > iter; void init(int v){ V = v; G.resize(V); } //directed graph void add_edge(int from,int to,int cap){ G[from].push_back( FLOW::make_edge_flow(to,cap,G[to].size()) ); G[to].push_back( FLOW::make_edge_flow(from,0,G[from].size()-1) ); } private: //sから最短距離をBFSで計算する void bfs(int s){//許容量もチェックしている queue que; dist = vector(V,-1); dist[s] = 0; que.push(s); while(!que.empty()){ int v = que.front();que.pop(); for(int i=0;i<(int)G[v].size();++i){ edge_flow &e = G[v][i]; if( e.cap > 0 && dist[e.to] < 0 ){ dist[e.to] = dist[v] + 1; que.push(e.to); } } } } private: //増加パスをDFSで探す int dfs(int v,int t,int f){ if( v==t ) return f; for(int &i = iter[v];i<(int)G[v].size();++i){//? FLOW::edge_flow &e = G[v][i]; if( e.cap>0 && dist[v] < dist[e.to]){ int d = this->dfs(e.to, t, min(f,e.cap) ); if( d > 0){ e.cap -= d; G[e.to][e.rev].cap += d; return d; } } } return 0; } public: //sからtへの最大流量を求める int max_flow(int s,int t){ int flow = 0; for(;;){ this->bfs(s); if( dist[t] < 0 ) return flow; iter = vector(V,0); int f; while( (f = this->dfs(s,t,INF) ) > 0 ){ flow += f; } } } }; } #pragma endregion //dinic :O(|E||V|^2) #pragma region //グラフ bool is_bipartite(int v,int c,vector< vector >& G,vector& Color){ Color[v] = c; for(int i=0;i < (int)G[v].size();++i){//隣接グラフ if(Color[ G[v][i] ] == c ) return false; if(Color[ G[v][i] ] == 0 && !is_bipartite(G[v][i],-c,G,Color) ){ return false; } } return true; } bool is_bipartite(int Root,vector< vector >& Graph){ int GraphSize = Graph.size(); vector Color(GraphSize,0); const int ColorNo = 1; return is_bipartite(Root,ColorNo,Graph,Color); } #pragma endregion //二部グラフチェック is_bipartite(root,GraphList) #pragma endregion // #pragma region //http://sugarknri.hatenablog.com/entry/2016/07/16/165715 void makeinv(vector& inv,const LL P){ int i; const int varMAX = 1000000; inv = vector( varMAX+1,0); inv[1]=1; for(i=2;i<=varMAX;i++){ inv[i] = (inv[P%i] * (P-P/i)%P ) % P;//OVF //inv[i] = powMod(i,P-2,P); } } LL nCk(LL N,LL k,LL mod = MOD){ static vector inv;//modの逆元 if( inv.size() == 0 ){ makeinv(inv,mod);//modは素数を入れる } k = min(k,N-k); if( k < 0 ){return 0;} if( k == 0 ){return 1;} if( k == 1 ){return N%mod;} LL ret = 1; for(int i=1;i<=k;++i){ ret = (ret * ((N+1-i)%mod) )%mod;//ret*N:OVF ret = (ret * inv[i] )%mod; //ret *= ((N+1-i)*inv[i])%mod;//OVF //ret %= mod; } return ret; } LL nCk_once(LL N,LL k,LL mod = MOD){//modは素数 k = min(k,N-k); if( k < 0 ){return 0;} if( k == 0 ){return 1;} if( k == 1 ){return N%mod;} LL ret = 1; LL A=1; for(LL i=0;i > NCK; LL nCk_base(int N,int K,LL mod=MOD){ K = min(K,N-K); if( K==0 ){return 1%mod;} if( K==1 ){return N%mod;}//%MOD; if( N<=10000 && NCK[N][K] ){ return NCK[N][K]; } //N個目を使わない:nCk(N-1,k) //N個目を使う :nCk(N-1,k-1) LL ans = (nCk_base(N-1,K)+nCk_base(N-1,K-1) )%mod;//%MOD; if( N<=10000 ){ NCK[N][K] = ans; } return ans; } #pragma endregion //組み合わせ メモ? #pragma region CGL class Point{ public: double x,y; Point(double x=0,double y=0):x(x),y(y){} Point operator + (Point p){return Point(add(x,p.x),add(y,p.y));} void operator += (Point p){x=add(x,p.x);y=add(y,p.y);} Point operator - (Point p){return Point(add(x,-p.x),add(y,-p.y));} void operator -= (Point p){x=add(x,-p.x);y=add(y,-p.y);} Point operator * (double a){return Point(x*a,y*a);} double operator * (Point p){return dot(p);} Point operator / (double a){return Point(x/a,y/a);} double norm(){return sqrt(x*x+y*y);} double dot(Point p){return add(x*p.x,y*p.y);} double rot(Point p){return add(x*p.y,-y*p.x);} double add(double a,double b){ double EPS = 1e-10; if( abs(a+b) < EPS*(abs(a)+abs(b)) ){ return 0; } return a+b; } }; istream& operator>>(istream& in,Point& P){ in >> P.x >> P.y; return in; } bool operator<(Point A,Point B){ if( A.x < B.x ) return true; else if( A.x > B.x ) return false; if( A.y < B.y ) return true; return false; } //線分で表した直線の交差判定 bool is_cross(Point p1,Point p2,Point q1,Point q2){ double res = (p2-p1).rot(q2-q1); return res != 0;//平行なら0 } /*ccwへ//線分p1-p2上に点qがあるか判定 bool on_seg(Point p1,Point p2,Point q){ return (p1-q).rot(p2-q) == 0 && (p1-q).dot(p2-q) <= 0; }*/ //直線p1-p2と直線q1-q2の交点 //交差判定をしてから使う:0除算 Point intersection(Point p1,Point p2,Point q1,Point q2){ return p1+(p2-p1)*((q2-q1).rot(q1-p1)/(q2-q1).rot(p2-p1)); } //線分ABに対する点C enum PointPotion{ONLINE_BACK=-2,CLOCKWISE,ON_SEGMENT,COUNTER_CLOCKWISE,ONLINE_FRONT}; PointPotion ccw(Point A,Point B,Point C){ B -= A;C -=A; if( B.rot(C) > 0 ) return COUNTER_CLOCKWISE;//+1 if( B.rot(C) < 0 ) return CLOCKWISE;//-1 if( B.dot(C) < 0 ) return ONLINE_BACK;//-2 if( B.norm() < C.norm() ) return ONLINE_FRONT;//+2 return ON_SEGMENT;//0 } //線分p1-p2,と線分q1-q2の交差判定 //http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_B bool intersect(Point p1,Point p2,Point q1,Point q2){ return (ccw(p1,p2,q1) * ccw(p1,p2,q2) <= 0) && (ccw(q1,q2,p1) * ccw(q1,q2,p2) <= 0); } /// //直線p1-p2と点q1の距離 double dist_LineP(Point p1,Point p2,Point q1){ return abs( (p2-p1).rot(q1-p1) )/(p2-p1).norm(); } //線分p1-p2と点q1の距離 double dist_SegP(Point p1,Point p2,Point q1){ //(日) if( (p2-p1).dot(q1-p1) < 0 ){ return (q1-p1).norm();//p1から見てp2と逆方向 } if( (p1-p2).dot(q1-p2) < 0 ){ return (q1-p2).norm();//p2から見てp1と逆方向 } return dist_LineP(p1,p2,q1);//垂線下ろす } // 線分同士の最短距離 //http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_D //http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=862507#1 double dist_segseg(Point A1,Point A2,Point B1,Point B2){ if( intersect(A1,A2,B1,B2) ){ return 0; } return min( min(dist_SegP(A1,A2,B1), dist_SegP(A1,A2,B2) ), min(dist_SegP(B1,B2,A1), dist_SegP(B1,B2,A2) ) ); } #pragma endregion //class Point #pragma region CGL //多角形内なら2,線上なら1,外なら0 //http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_3_C //http://www.prefield.com/algorithm/geometry/contains.html //点Pから半直線を引く、ガウス int contains(vector& v,Point& P){ bool in = false; const int N = v.size(); for(int i=0;i B.y ) swap(A,B); if( A.y <= 0 && 0 < B.y ){ if( A.rot(B) < 0 ) in =!in; } if( A.rot(B) == 0 && A.dot(B) <= 0 ){ return 1;//ON 線上 } } return in ? 2:0;//中:外 } #pragma endregion //contains #pragma region CGL //辞書順で比較 bool cmp_x(const Point& p,const Point& q){ if( p.x != q.x ) return p.x < q.x; return p.y < q.y; } //凸包を求める vector convex_hull(vector ps,int n){ sort(ps.begin(),ps.end(), cmp_x); int k = 0;//凸包の頂点数 vector qs(n*2);//構築中の凸包 //下側の凸包の作成 for(int i=0;i1 && (qs[k-1]-qs[k-2]).rot(ps[i]-qs[k-1]) <=0){//<で線上も加える k--; } qs[k++] = ps[i]; } //上側凸包の作成 for(int i=n-2,t=k;i>=0;i--){ while(k>t && (qs[k-1]-qs[k-2]).rot(ps[i]-qs[k-1]) <=0){//< k--; } qs[k++] = ps[i]; } qs.resize(k-1); return qs; } #pragma endregion //凸包 #pragma region DSL #pragma region DSL class UnionFind{ public: int cNum;//要素数 vector parent; vector count; vector< vector > GList; UnionFind(int n){ cNum = n; parent = vector(n); count = vector(n,1); GList.resize(n); for(int i=0;i dat; public: int getN(){return n;} void init(int size,int num=INF,int num_null=-1){//N:要素数,最大値 OTHER_VAL = num; NUM_NULL = num_null; n = 2; while(n < size ){ n <<= 1; } dat.assign(n<<1, OTHER_VAL ); } void init(vector vec,int size,int num=INF){ OTHER_VAL = num; n = 2; while(n < size ){ n <<= 1; } dat.assign(n<<1,OTHER_VAL ); for(int i=0;i>= 1; } } void update(int X,int Y,int VAL){ //全体の範囲は閉区間、 update(1,0,n-1,X,Y,VAL); } private: void update(int t,int L,int R,int X,int Y,int VAL){ //親から子へ進んでいく if( L == X && R == Y){ dat[t] = VAL; }else{ int mid = (L+R)/2; if( dat[t] != NUM_NULL ){//値の伝播 dat[t*2+0] = dat[t]; dat[t*2+1] = dat[t]; dat[t] = NUM_NULL; } if( Y <= mid ){ update(t*2+0,L,mid,X,Y,VAL); }else if( X > mid ){ update(t*2+1,mid+1,R,X,Y,VAL); }else{ update(t*2+0,L,mid,X,mid,VAL); update(t*2+1,mid+1,R,mid+1,Y,VAL); } } } public: //query(a,b,0,0,n)//[a,b)半開区間 int query(int a,int b){ return query(a,b,1,0,n);//n==getNを使う } private: int query(int a,int b,int k,int l,int r){ if(r<=a || b<=l)return OTHER_VAL;//交差しない if(a<=l && r<=b && dat[k]!=NUM_NULL)return dat[k]; int res = OTHER_VAL; int mid = (l+r)>>1; if( a < mid ) res = SELECT(res,query(a,b,k*2+0,l,mid) ); if( mid < b ) res = SELECT(res,query(a,b,k*2+1,mid,r) ); return res; } }; #pragma endregion //segment tree #pragma region DSL class BITree{//1-index int N; vector bit; public: BITree(int n){ N = n; bit = vector(N+1,0);//1-index } void add(int a,LL w){ for(int i=a;i<=N;i += i & -i){ bit[i] += w; } } LL sum(int a){//[1,a)の和 LL ret = 0; for(int i=a; i > 0; i -= i & -i){ ret += bit[i]; } return ret; } }; #pragma endregion //BIndexTree #pragma endregion // #pragma region template istream& operator>>(istream& in,pair& P){ in >> P.first >> P.second; return in; } #pragma endregion //cin pair #pragma region template istream& operator>>(istream& in,vector& v){ int size = v.size(); for(int i=0;i> v[i]; } return in; } #pragma endregion //cin vector #pragma region //行列の積 template vector< vector > operator*( vector >& A,vector< vector >& B){ LL mod = MOD; int R = A.size(); int cen = A[0].size(); int C = B[0].size(); vector< vector > ans(R,vector(C,0) ); for(int row=0;row vector< vector > powMod(vector< vector > mat,LL N){ int R = mat.size(); int C = mat[0].size(); //R==C vector< vector > I(R,vector(C,0));//単位元 for(int i=0;i > mul(R,vector(C)),ans(R,vector(C)); ans = I; mul = mat; while(N){ if( N & 1 ){ ans = ans*mul; } N >>= 1; mul = mul*mul; } return ans; } #pragma endregion //行列 #pragma region namespace TIME{ time_t start,limit; void time_start(){start = time(NULL);} void time_set(int num){limit = num;}//秒 bool check(){return (time(NULL)-start < limit);} } #pragma endregion //時間計測 /* #pragma region namespace RAND{ mt19937 mt; void rand_init(){ random_device rnd; mt = mt19937(rnd()); } int rand(){ return mt(); } } #pragma endregion //乱数 */ #pragma region #pragma endregion // //////////////////// #pragma region double area(vector poly){ int size = poly.size(); double ans = 0; for(int i=1;i::iterator itr,int N){ if( N <= 1 ) return INF; int m = N/2; double x = (itr+m)->x; double d = min(closest_pair(itr,m), closest_pair((itr+m),N-m) ); inplace_merge(itr,itr+m,itr+N,compare_y); vector B; for(int i=0;ix - x) >= d) continue; int Bsize = B.size(); for(int j=0;jx - B[Bsize-j-1].x; dy = (itr+i)->y - B[Bsize-j-1].y; if( dy >= d ) break; d = min(d,hypot(dx,dy)); } B.push_back(*(itr+i)); } return d; } #pragma endregion //最近対 2D //////////////////// #pragma region int CircleIntersection(Point A,double AR,Point B,double BR){ double D = (B-A).norm(); if( D > AR+BR ){ return 4; }else if( D == AR+BR ){ return 3; }else if( abs(AR-BR) < D ){//&& D CircleLine(Point C,double CR,Point A,Point B){ vector ans(2);//同じ交点なら同じ値 double a,b,c; a = -(A.y-B.y); b = A.x-B.x; c = -(a*A.x+b*A.y); double l,k,d; l = a*a+b*b; k = a*C.x + b*C.y+ c; d = l*CR*CR-k*k; if(d>0){ double ds = sqrt(d); double apl = a/l; double bpl = b/l; double xc = C.x-apl*k; double yc = C.y-bpl*k; double xd = bpl*ds; double yd = apl*ds; Point temp; ans[0].x = xc-xd; ans[0].y = yc+yd; ans[1].x = xc+xd; ans[1].y = yc-yd; }else if(d==0){ Point temp; temp.x = C.x-a*k/l; temp.y = C.y-b*k/l; ans[0] = temp; ans[1] = temp; }else{ Point temp; temp.x = INF; temp.y = INF; ans[0] = temp; ans[1] = temp; } return ans; } #pragma endregion //円と直線の交点,距離チェックする。 ////////////////// //行列式 ///////////////// void solve(){ int N,M; cin >> N >> M; vector A(N-1); LL AAA; cin >> AAA; for(int i=0;i> A[i]; } sort(A.begin(), A.end()); int NG = -1; int OK = N-1; int mid; while(OK-NG>1){ mid = (OK+NG)/2; if( mid < 0 || N-2 < mid ) break; int ter = A[mid] + AAA; int pos = -1; int count = 0; for(int i=N-2;i>=0;--i){ if( i == mid) continue; ++pos; for(;pos ter ){ ++count; break; } } if( count > M ){ break; } } if( count > M ){ NG = mid; }else{ OK = mid; } } if( 0<= OK && OK < N-1 ){ cout << A[OK] << endl; }else{ cout << -1 << endl; } } #pragma region main signed main(void){ std::cin.tie(0); std::ios::sync_with_stdio(false); std::cout << std::fixed;//小数を10進数表示 cout << setprecision(16);//小数点以下の桁数を指定//coutとcerrで別 solve(); } #pragma endregion //main()