A medicament characterized in that (A) a compound represented by the formula (I): , its pharmaceutically acceptable salt, or a solvate thereof, wherein P is hydrogen or a group to form a prodrug； A 1 is CR 1A R 1B , S or O； A 2 is CR 2A R 2B , S or O； A 3 is CR 3A R 3B , S or O； A 4 is each independently CR 4A R 4B , S or O； the number of hetero atoms among atoms constituting the ring which consists of A 1 , A 2 , A 3 , A 4 , nitrogen atom adjacent to A 1 and carbon atom adjacent to A 4 is 1 or 2； R 1A and R 1B are each independently hydrogen, halogen, alkyl or the like； R 2A and R 2B are each independently hydrogen, halogen, alkyl, or the like； R 3A and R 3B are each independently hydrogen, halogen, alkyl, or the like； R 4A are each independently hydrogen, halogen, alkyl, or the like； R 4B are each independently hydrogen, halogen, alkyl, or the like； R 3A and R 3B may be taken together with an adjacent carbon atom to form non-aromatic carbocycle or non-aromatic heterocycle； n is any integer of 1 to 2； and R 1 is or the like, is combined with (B) compound(s) having an anti-influenza activity, its pharmaceutically acceptable salt or a solvate thereof and/or an antibody having anti-influenza activity, is useful for treating or preventing influenza.
