Compilare: user.cpp: In function ‘int dijkstra(bool)’: user.cpp:73:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < ans.size(); ++ i) ~~^~~~~~~~~~~~ user.cpp:74:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] fout << ans[i] << " \n"[i + 1 == ans.size()]; ~~~~~~^~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:113:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < primes.size(); ++ i) { ~~^~~~~~~~~~~~~~~ user.cpp: In function ‘int dijkstra(bool)’: user.cpp:87:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:10:43: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In member function ‘void InputReader::advance()’: user.cpp:33:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^