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