Cho da~y s g`m n s nguyn a1, a2, , an. 
Ti`m gia tri? lon nht cu?a ha`m f(i,j,k)= ai+2*aj+3*ak voi 1<=i<j<k<=n
Vi du? : voi da~y g`m 5 s -1, 2, -2, -3, 5 thi` f(1,2,5)=-1+2*2+3*5=18 la` lon nht.
Du~ li?u va`o : tu` File van ba?n SEQUENCE.INP
-do`ng d`u tin chua s nguyn n (3<=n<=10^5)
-do`ng thu i trong n do`ng tip theo chua s nguyn ai (|ai|<=10^9)
Kt qua? : dua ra File van ba?n SEQUENCE.OUT 1 s nguyn- gia tri? lon nht cu?a ha`m f(i,j,k) ti`m dc
Vi du? : 
SEQUENCE.INP
5
-1
2
-2
-3
5
SEQUENCE.OUT
18
