Compilare: user.cpp: In function ‘int main()’: 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 ("concert2.in","r",stdin); ^ user.cpp:25:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("concert2.out","w",stdout); ^ user.cpp:26:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%hi%hi%hi",&n,&k1,&k2); ^ user.cpp:27:59: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for (i=1;i<=n;i++) scanf("%i",&a[i]),v.push_back(a[i]); ^