Compilare: user.cpp: In function ‘void read()’: user.cpp:19: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result user.cpp: In function ‘int df_sum(int)’: user.cpp:34: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void df_rev(int, int)’: user.cpp:53: warning: comparison between signed and unsigned integer expressions