Compilare: user.cpp: In function ‘int main()’: user.cpp:25:9: warning: unused variable ‘a’ [-Wunused-variable] int a,b,n,i; ^ user.cpp:25:11: warning: unused variable ‘b’ [-Wunused-variable] int a,b,n,i; ^ user.cpp:23:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hacker3.in","r",stdin); ^ user.cpp:24:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hacker3.out","w",stdout); ^ user.cpp:26:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:28:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&v[i].a,&v[i].b); ^