Compilare: user.cpp: In function ‘void pop_fronto(char&)’: user.cpp:32:9: warning: variable ‘flag’ set but not used [-Wunused-but-set-variable] int flag = 0; ^ user.cpp:34:10: warning: variable ‘st2’ set but not used [-Wunused-but-set-variable] char st2; ^ user.cpp: In function ‘int main()’: user.cpp:90:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("queue.in", "r", stdin); ^ user.cpp:91:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("queue.out", "w", stdout); ^ user.cpp:98:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^