Compilare: user.cpp: In function ‘int main()’: user.cpp:65:15: warning: left operand of comma operator has no effect [-Wunused-value] switch(b[i],b[n+1-i]); ^ user.cpp:40:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("next.in","r",stdin); ^ user.cpp:41:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("next.out","w",stdout); ^ user.cpp:47:11: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir); ^ user.cpp:53:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", & d); ^ /tmp/cctULljh.o: In function `main': user.cpp:(.text.startup+0x92): warning: the `gets' function is dangerous and should not be used.