2a

n=int(input())
a=[]
maxx=-1
for i in range(n):
    a += [int(input())]
for i in range(n):
    for j in range(n):
        if(a[i]*a[j])%14==0 and a[i]*a[j]>maxx:
            if i != j:
                maxx=a[i]*a[j]
print(maxx)