Compilare: main.cpp: In function 'int main()': main.cpp:123:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < things.size(); i++) { ~~^~~~~~~~~~~~~~~ main.cpp:91:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("engineer.in", "r", stdin); ^ main.cpp:92:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("engineer.out", "w", stdout); ^