Compilare: user.cpp: In function ‘int op_A(int, int)’: user.cpp:38:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘void read_data()’: user.cpp:27:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:29:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &v[i]); ^ user.cpp: In function ‘int main()’: user.cpp:51:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &op, &a, &b); ^