Compilare: user.cpp: In function ‘int main()’: user.cpp:17:30: warning: format ‘%lf’ expects argument of type ‘double*’, but argument 2 has type ‘long double*’ [-Wformat=] scanf("%lf %lf", &x1, &y1); ^ user.cpp:17:30: warning: format ‘%lf’ expects argument of type ‘double*’, but argument 3 has type ‘long double*’ [-Wformat=] user.cpp:21:34: warning: format ‘%lf’ expects argument of type ‘double*’, but argument 2 has type ‘long double*’ [-Wformat=] scanf("%lf %lf", &x2, &y2); ^ user.cpp:21:34: warning: format ‘%lf’ expects argument of type ‘double*’, but argument 3 has type ‘long double*’ [-Wformat=] user.cpp:29:20: warning: format ‘%lf’ expects argument of type ‘double’, but argument 2 has type ‘long double’ [-Wformat=] printf("%lf", a); ^ user.cpp:14:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("aria.in","r",stdin); ^ user.cpp:15:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("aria.out","w",stdout); ^ user.cpp:16:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:17:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf", &x1, &y1); ^ user.cpp:21:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf", &x2, &y2); ^