import sys
input = lambda : sys.stdin.readline().rstrip()
sys.setrecursionlimit(max(1000, 10**9))
write = lambda x: sys.stdout.write(x+"\n")


n = int(input())
a = list(map(int, input().split()))
if 0 in a:
    ans = -1
else:
    v = 1
    for k in a:
        if k==1:
            pass
        elif k>=4:
            ans = M
            break
        else:
            d = [1,1,2,6]
            v *= pow(k, d[k])
            if v>M:
                ans = M
                break
    else:
        ans = M%v
print(ans)