Compilare: user.cpp: In function ‘int main()’: user.cpp:31:6: warning: unused variable ‘op’ [-Wunused-variable] int op, x, y; ^ user.cpp:31:10: warning: unused variable ‘x’ [-Wunused-variable] int op, x, y; ^ user.cpp:31:13: warning: unused variable ‘y’ [-Wunused-variable] int op, x, y; ^ user.cpp:33:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.in","r",stdin); ^ user.cpp:34:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apm.out","w",stdout); ^ user.cpp:36:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:39:47: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &u[i].a, &u[i].b, &u[i].c); ^