#define _USE_MATH_DEFINES #include #include #include #include #include #include //#include #include #include #include #include #include #include ///////// #define REP(i, x, n) for(int i = x; i < n; i++) #define rep(i,n) REP(i,0,n) #define P(p) cout<<(p)< ///////// typedef long long LL; typedef long double LD; ///////// using namespace::std; ///////// int main(void){ std::cin.tie(0); std::ios::sync_with_stdio(false); std::cout << std::fixed;// //cout << setprecision(16);// int N,M; cin>>N>>M; int L,R; vector< vector > vec; vector temp(2); rep(i,N){ cin>> L >> R ; if( L < M-1-R ){ temp[0] = L; temp[1] = R; }else{ temp[0] = M-1-R; temp[1] = M-1-L; } vec.push_back(temp); } sort( vec.begin(), vec.end() ); bool col[4000]; rep(i,M) col[i] = false; bool ret = false; int ans = 1; rep(i,N){ L = vec[i][0]; R = vec[i][1]; ret = true; //そのまま for(int j = L; j <= R; ++j){ if( col[j] != false ){ ret = false; break; } } if( ret == true ){ for(int j = L; j <= R; ++j){ col[j] = true;//塗る } } else if( ret == false ){//反転チェック ret = true; for(int j = L; j <= R; ++j){ if( col[M-1-j] != false ){ ret = false; break; } } if( ret == true ){ for(int j = L; j <= R; ++j){ col[M-1-j] = true;//塗る } } } if( ret == false ){ P("NO"); return 0; } } P("YES"); return 0; }