Compilare: user.cpp: In function ‘int main()’: user.cpp:44:13: warning: unused variable ‘a’ [-Wunused-variable] int a,b,c,d; ^ user.cpp:44:15: warning: unused variable ‘b’ [-Wunused-variable] int a,b,c,d; ^ user.cpp:44:17: warning: unused variable ‘c’ [-Wunused-variable] int a,b,c,d; ^ user.cpp:44:19: warning: unused variable ‘d’ [-Wunused-variable] int a,b,c,d; ^ user.cpp:38:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.in","r",stdin); ^ user.cpp:39:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.out","w",stdout); ^