foo.cc: In function ‘int main()’:
foo.cc:38:35: warning: left operand of comma operator is a reference, not call, to function ‘std::ios_base::sync_with_stdio’ [-Waddress]
   38 |     ios::sync_with_stdio,cin.tie(0),cout.tie(0);
      |                                   ^
foo.cc:38:35: warning: left operand of comma operator has no effect [-Wunused-value]