Compilare: user.cpp: In function ‘void write()’: user.cpp:59:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<order.size(); ++i) ^ user.cpp: In function ‘void read()’: user.cpp:25:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &N, &M); ^ user.cpp:29:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &op); ^