/** * code generated by JHelper * More info: https://github.com/AlexeyDmitriev/JHelper * @author */ #ifndef SOLUTION_COMMON_H #include using namespace std; using ll = long long; using PI = pair; template using V = vector; using VI = V; #define _1 first #define _2 second #ifdef MY_DEBUG # define DEBUG(x) x #else # define DEBUG(x) #endif template std::ostream & operator <<(ostream &os, const pair &p) { os << "(" << p._1 << "," << p._2 << ")"; return os; } template inline void debug(T &A) { DEBUG( for (const auto &a : A) { cerr << a << " "; } cerr << '\n'; ) } template inline void debug_with_format(T &A, Func f) { DEBUG( for (const auto &a : A) { cerr << f(a) << " "; } cerr << '\n'; ) } template inline void debug_dim2(T &A) { DEBUG( for (const auto &as : A) { debug(as); } ) } template inline void debug(const char *format, Args const &... args) { DEBUG( fprintf(stderr, format, args ...); cerr << '\n'; ) } template string format(const string &fmt, Args ... args) { size_t len = snprintf(nullptr, 0, fmt.c_str(), args ...); vector buf(len + 1); snprintf(&buf[0], len + 1, fmt.c_str(), args ...); return string(&buf[0], &buf[0] + len); } template string fmtP(pair a) { stringstream ss; ss << "(" << a._1 << "," << a._2 << ")"; return ss.str(); } #define SOLUTION_COMMON_H #endif //SOLUTION_COMMON_H const int MOD = 1000000007; class D { public: void solve(std::istream& in, std::ostream& out) { ios::sync_with_stdio(false); cin.tie(nullptr); int h, w; in >> h >> w; V> g(h, V(w)); for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) { in >> g[i][j]; } } debug_dim2(g); bool row = false; // 白黒が全部いっしょの行があった for (int i = 0; i < h; ++i) { bool same = true; for (int j = 1; j < w; ++j) { same &= g[i][j] == g[i][j - 1]; } if (same) row = true; } bool col = false; // 全部一緒の列があった for (int j = 0; j < w; ++j) { bool same = true; for (int i = 1; i < h; ++i) { same &= g[i][j] == g[i - 1][j]; } if (same) col = true; } debug("%d %d", row, col); if (row && h > 1 && col && w > 1) { out << "NO"; } else { out << "YES"; } } }; int main() { D solver; std::istream& in(std::cin); std::ostream& out(std::cout); solver.solve(in, out); return 0; }