Compilare: user.cpp: In function ‘int main()’: user.cpp:6:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("lantaditiv.in", "r",stdin); ^ user.cpp:7:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("lantaditiv.out", "w",stdout); ^ user.cpp:9:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &an); ^