chessboard.cpp: In function 'int main()':
chessboard.cpp:26:13: warning: unused variable 'l' [-Wunused-variable]
26 | int l = n/i;
| ^
chessboard.cpp: In function 'void IO(std::string)':
chessboard.cpp:11:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
chessboard.cpp:11:70: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~