Compilare: user.cpp: In function ‘int main()’: user.cpp:30:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("melc.in","r",stdin); ^ user.cpp:31:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("melc.out","w",stdout); ^ user.cpp:33:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf\n",&a[0],&b[0]); ^ user.cpp:35:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&n); ^ user.cpp:41:47: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf %d ",&a[i],&b[i],&c[i]); ^