#pragma GCC optimize ("O3") #pragma GCC target ("avx") #include "bits/stdc++.h" // define macro "/D__MAI" using namespace std; typedef long long int ll; #define debugv(v) printf("L%d %s => ",__LINE__,#v);for(auto e:v){cout< ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout< ostream& operator <<(ostream &o, const pair p) { o << "(" << p.first << ":" << p.second << ")"; return o; } #define TIME chrono::system_clock::now() #define MILLISEC(t) (chrono::duration_cast(t).count()) namespace { std::chrono::system_clock::time_point ttt; void tic() { ttt = TIME; } void toc() { fprintf(stderr, "TIME : %lldms\n", MILLISEC(TIME - ttt)); } std::chrono::system_clock::time_point tle = TIME; #ifdef __MAI void safe_tle(int msec) { assert(MILLISEC(TIME - tle) < msec); } #else #define safe_tle(k) ; #endif } #ifdef __MAI #define getchar_unlocked getchar #define putchar_unlocked putchar #endif #ifdef __VSCC #define getchar_unlocked _getchar_nolock #define putchar_unlocked _putchar_nolock #endif namespace { #define isvisiablechar(c) (0x21<=(c)&&(c)<=0x7E) class MaiScanner { public: template void input_integer(T& var) { var = 0; T sign = 1; int cc = getchar_unlocked(); for (; cc<'0' || '9'>(int& var) { input_integer(var); return *this; } inline MaiScanner& operator>>(long long& var) { input_integer(var); return *this; } inline MaiScanner& operator>>(string& var) { int cc = getchar_unlocked(); for (; !isvisiablechar(cc); cc = getchar_unlocked()); for (; isvisiablechar(cc); cc = getchar_unlocked()) var.push_back(cc); } }; class MaiPrinter { int stack_p; char stack[32]; public: template void output_integer(T var) { if (var == 0) { putchar_unlocked('0'); return; } if (var < 0) { putchar_unlocked('-'); var = -var; } stack_p = 0; while (var) { stack[stack_p++] = '0' + (var % 10); var /= 10; } while (stack_p) putchar_unlocked(stack[--stack_p]); } MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; } MaiPrinter& operator<<(int var) { output_integer(var); return *this; } MaiPrinter& operator<<(long long var) { output_integer(var); return *this; } MaiPrinter& operator<<(const string& str) { const char* p = str.c_str(); const char* l = p + str.size(); while (p < l) putchar_unlocked(*p++); return *this; } }; } MaiScanner scanner; MaiPrinter printer; // ---------------------------------------------------- // 答案ここから // --------------------------------------------------- void connect(int u, int v) { printer << (u + 1) << ' ' << (v + 1) << '\n'; } int main() { ll n, m; scanner >> n >> m; // 二部グラフの頂点数na, n-na // 完全二部グラフを考えたとき,辺の数が最も多くなるようなna, nbを求める.(na < nb) ll na = n/2; ll mbest = na*(n-na); // 入力から与えられたmが範囲内かどうか調べる. if (m < n - 1 || mbest < m) { cout << "NO" << endl; return 0; } printer << "YES \n"; // 頂点に書き込まれる値 = 頂点noとする. repeat(n) { printer << (cnt + 1) << ' '; } printer << '\n'; // 連結にするための最小限の辺を引く. connect(0, na); --m; iterate(1, na) { connect(cnt, na + cnt - 1); connect(cnt, na + cnt); m -= 2; } iterate(na*2, n) { connect(na - 1, cnt); m -= 1; } // 残りの辺を加える. int ai = 0; int bi = 1; repeat(m) { if (ai == bi || ai == bi + 1) { --cnt; // redo } else { connect(ai, na + bi); } // インクリメント if (++bi >= n - na) { ++ai; bi = 0; } } return 0; }