Compilare: user.cpp: In function ‘int main()’: user.cpp:8:11: warning: variable ‘fin’ set but not used [-Wunused-but-set-variable] FILE *fin, *fout; ^~~ user.cpp:8:17: warning: variable ‘fout’ set but not used [-Wunused-but-set-variable] FILE *fin, *fout; ^~~~ user.cpp:11:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld", &N); ^ user.cpp:13:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld", &a, &b); ^