Compilare: user.cpp: In function ‘int main()’: user.cpp:49:17: warning: unused variable ‘x’ [-Wunused-variable] int x=0; ^ user.cpp:66:21: warning: unused variable ‘x’ [-Wunused-variable] int x=0; ^ user.cpp:74:21: warning: unused variable ‘x’ [-Wunused-variable] int x=0; ^ user.cpp:41:34: 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:42:36: 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:44:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); gets(s); ^ user.cpp:44:28: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); gets(s); ^ user.cpp:47:18: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s+1); ^ /tmp/ccIgHz1f.o: In function `main': user.cpp:(.text.startup+0x6a): warning: the `gets' function is dangerous and should not be used.