Compilare: user.cpp: In function ‘int pinex(int, int)’: user.cpp:21:15: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] int ans = NULL, ^ user.cpp: In function ‘int main()’: user.cpp:69:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("farey.in", "r", stdin); ^ user.cpp:70:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("farey.out", "w", stdout); ^