Compilare: user.cpp: In function ‘int main()’: user.cpp:5:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cal.in","r",stdin); ^ user.cpp:6:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cal.out","w",stdout); ^ user.cpp:8:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld%ld%ld",&x,&y,&S,&n); ^ user.cpp:11:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld%ld",&a,&b); ^