Compilare: user.cpp:2:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main(){long long N,P=1;freopen("fetite.in","r",stdin);freopen("fetite.out","w",stdout);scanf("%lld",&N);while(P-1<N)P*=2;printf("%lld",((N-(P/2)+1)*2)-1);} ^ user.cpp: In function ‘int main()’: user.cpp:2:54: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] main(){long long N,P=1;freopen("fetite.in","r",stdin);freopen("fetite.out","w",stdout);scanf("%lld",&N);while(P-1<N)P*=2;printf("%lld",((N-(P/2)+1)*2)-1);} ^ user.cpp:2:87: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] main(){long long N,P=1;freopen("fetite.in","r",stdin);freopen("fetite.out","w",stdout);scanf("%lld",&N);while(P-1<N)P*=2;printf("%lld",((N-(P/2)+1)*2)-1);} ^ user.cpp:2:104: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] main(){long long N,P=1;freopen("fetite.in","r",stdin);freopen("fetite.out","w",stdout);scanf("%lld",&N);while(P-1<N)P*=2;printf("%lld",((N-(P/2)+1)*2)-1);} ^