Compilare: main.cpp: In function 'void write_output_to_file()': main.cpp:47:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= N; ++i) ~~^~~~ main.cpp:49:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j <= N; ++j) ~~^~~~ main.cpp:51:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (!guards_pos.empty() && i == guards_pos.front().first && j == guards_pos.front().second) ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:51:75: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (!guards_pos.empty() && i == guards_pos.front().first && j == guards_pos.front().second) ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~