Compilare: user.cpp: In function ‘int main()’: user.cpp:24:11: warning: unused variable ‘u’ [-Wunused-variable] int n,i,j,u=0,vertical=0; ^ user.cpp:24:15: warning: unused variable ‘vertical’ [-Wunused-variable] int n,i,j,u=0,vertical=0; ^ user.cpp:22:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.in","r",stdin); ^ user.cpp:23:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.out","w",stdout); ^ user.cpp:26:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:29:39: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&v[i].first,&v[i].second); ^