foo.cc:2:21: error: expected unqualified-id before '!' token
    2 | using namespace std;![](http://)
      |                     ^
foo.cc: In function 'bool dfs(int)':
foo.cc:15:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |     for (int j = 0; j < edges[i].size(); j++) {
      |                     ~~^~~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:31:21: error: 'n' was not declared in this scope; did you mean 'yn'?
   31 |     scanf("%d %d", &n, &m);
      |                     ^
      |                     yn
foo.cc:31:25: error: 'm' was not declared in this scope
   31 |     scanf("%d %d", &n, &m);
      |                         ^
foo.cc:43:27: warning: suggest parentheses around comparison in operand of '^' [-Wparentheses]
   43 |             if (arr[i][j] == 1 ^ (((i + j) & 1) == ((x + y) & 1)))
      |                 ~~~~~~~~~~^~~~

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