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; A1 is CR1AR1B, S or O; A2 is CR2AR2B, S or O; A3 is CR3AR3B, S or O; A4 is each independently CR4AR4B, S or O; the number of hetero atoms among atoms constituting the ring which consists of A1, A2, A3, A4, nitrogen atom adjacent to A1 and carbon atom adjacent to A4 is 1 or 2; R1A and R1B are each independently hydrogen, halogen, alkyl or the like; R2A and R2B are each independently hydrogen, halogen, alkyl, or the like; R3A and R3B are each independently hydrogen, halogen, alkyl, or the like; R4A are each independently hydrogen, halogen, alkyl, or the like; R4B are each independently hydrogen, halogen, alkyl, or the like; R3A and R3B 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 R1 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.