Compilare: user.cpp: In function ‘void pref(int)’: user.cpp:30: warning: comparison between signed and unsigned integer expressions user.cpp:35: warning: unused variable ‘ok’ user.cpp: In function ‘int main()’: user.cpp:54: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:58: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:61: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:64: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result