#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<\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout< ostream& operator <<(ostream &o, const pair p) { o << "(" << p.first << ":" << p.second << ")"; return o; } template T& maxset(T& to, const T& val) { return to = max(to, val); } template T& minset(T& to, const T& val) { return to = min(to, val); } void bye(string s, int code = 0) { cout << s << endl; exit(0); } mt19937_64 randdev(8901016); inline ll rand_range(ll l, ll h) { return uniform_int_distribution(l, h)(randdev); } #if defined(_WIN32) || defined(_WIN64) #define getchar_unlocked _getchar_nolock #define putchar_unlocked _putchar_nolock #elif __GNUC__ #else #define getchar_unlocked getchar #define putchar_unlocked putchar #endif namespace { #define isvisiblechar(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 (; !isvisiblechar(cc); cc = getchar_unlocked()); for (; isvisiblechar(cc); cc = getchar_unlocked()) var.push_back(cc); } template void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; } }; class MaiPrinter { public: template void output_integer(T var) { if (var == 0) { putchar_unlocked('0'); return; } if (var < 0) putchar_unlocked('-'), var = -var; char stack[32]; int stack_p = 0; while (var) stack[stack_p++] = '0' + (var % 10), var /= 10; while (stack_p) putchar_unlocked(stack[--stack_p]); } inline MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; } inline MaiPrinter& operator<<(int var) { output_integer(var); return *this; } inline MaiPrinter& operator<<(long long var) { output_integer(var); return *this; } inline MaiPrinter& operator<<(const char* str_p) { while (*str_p) putchar_unlocked(*(str_p++)); return *this; } inline 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; } template void join(IT begin, IT end, char sep='\n') { for (auto it = begin; it != end; ++it) *this << *it << sep; } }; } 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) { printer << "NO" << '\n'; return 0; } printer << "YES \n"; // 頂点に書き込まれる値 = 頂点番号とする. for (int i = 0; i < n; ++i) { printer << (i + 1) << ' '; } printer << '\n'; // 連結にするための最小限の辺を引く. connect(0, na); --m; for (int i = 1; i < na; ++i) { connect(i, na + i - 1); connect(i, na + i); m -= 2; } for (int i = na*2; i < n; ++i) { connect(na - 1, i); m -= 1; } // 残りの辺を加える. int ai = 0; int bi = 1; while (0 < m) { if (ai != bi && ai != bi + 1) { connect(ai, na + bi); --m; } // インクリメント if (++bi >= n - na) { ++ai; bi = 0; } } return 0; }