n= int(input())
max2=-1
max13=-1
max26=-1
pos=0
pos2=0
pos3=0
maxx=-1
maxy=-1
for i in range(0,n):
    h=int(input())
    if h%26==0:
        if h>max26:
            max26=h
            pos=i
    elif h%13:
        if h>max13:
            max13=h
    elif h%2:
        if h>max2:
            max2=h
    if h>maxx:
       maxy=maxx
       pos2=i
    else:
      if h>maxy
         pos3=i
         maxy=h
if max26!=-1 and pos!=pos2:
     print(max26*maxx)
elif max26!=-1 and pos!=pos3:
     print(max26*maxy)
elif max13!=-1 and max2!=-1
     print(max13*max2)
else:
     print(0)