Compilare: user.cpp: In function ‘int main()’: user.cpp:3:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] {freopen ("suma.in","r",stdin); ^ user.cpp:4:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("suma.out","w",stdout); ^ user.cpp:6:15: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:21:6: warning: ‘k’ may be used uninitialized in this function [-Wmaybe-uninitialized] if((k*(k+1)/2-n)%2==0) ^