Compilare: user.cpp: In function ‘int main()’: user.cpp:75:7: warning: unused variable ‘a’ [-Wunused-variable] int a, b; ^ user.cpp:75:10: warning: unused variable ‘b’ [-Wunused-variable] int a, b; ^ user.cpp:72:28: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d %d", &N, &M); ^