Compilare: user.cpp: In function ‘int retine(int)’: user.cpp:30: warning: no return statement in function returning non-void user.cpp: In function ‘void back(int)’: user.cpp:38: warning: suggest explicit braces to avoid ambiguous ‘else’ user.cpp: In function ‘int main()’: user.cpp:50: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result