func_code_string: #include <bits/stdc++.h>   using namespace std;   const int maxn = 500010;   int n, m;   int pos[maxn];   int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};   inline void read(int &k) {     int f = 1;     k = 0;     char c = getchar();     while (c <  0  || c >  9 ) c ==  -  && (f = -1), c = getchar();     while (c <=  9  && c >=  0 ) k = k * 10 + c -  0 , c = getchar();     k *= f;   }   bool check(int i, int j) {     int x = (i - 1) / m + 1, y = (i - 1) % m + 1, x2 = (j - 1) / m + 1,         y2 = (j - 1) % m + 1;     for (int k = 0; k < 4; k++)       if (x + dx[k] == x2 && y + dy[k] == y2) return 1;     return 0;   }   bool dfs(int i) {     if (i == n * m + 1) return 1;     int x = (i - 1) / m + 1, y = (i - 1) % m + 1;     for (int j = i; j <= n * m; j++) {       swap(pos[i], pos[j]);       if (x != 1 && check(pos[i], pos[(x - 2) * m + y])) continue;       if (y != 1 && check(pos[i], pos[(x - 1) * m + y - 1])) continue;       if (dfs(i + 1)) return 1;       swap(pos[i], pos[j]);     }     return 0;   }   int main() {     read(n);     read(m);     for (int i = 1; i <= n; i++)       for (int j = 1; j <= m; j++) pos[(i - 1) * m + j] = (i - 1) * m + j;     if (!dfs(1)) return puts( NO ), 0;     puts( YES );     for (int i = 1; i <= n; i++, puts(  ))       for (int j = 1; j <= m; j++) printf( %d  , pos[(i - 1) * m + j]);   }   