Compilare: user.cpp: In function ‘int main()’: user.cpp:27:10: warning: unused variable ‘c’ [-Wunused-variable] char c; ^ user.cpp:28:20: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(a,N-1,in); ^ user.cpp:29:20: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(b,N-1,in); ^