#!/usr/bin/env python
#!-*- encoding: utf-8 -*-

import math
import re
import sys

def comb_gen(items, n=None):
    if n is None:
        n = len(items)
    for i in range(len(items)):
        v = items[i:i+1]
        if n == 1:
            yield v
        else:
            rest = items[i+1:]
            for c in comb_gen(rest, n-1):
                yield v + c

def perm_gen(items, n=None):
    if n is None:
        n = len(items)
    for i in range(len(items)):
        v = items[i:i+1]
        if n == 1:
            yield v
        else:
            rest = items[:i] + items[i+1:]
            for p in perm_gen(rest, n-1):
                yield v + p

def sum_element(lst):
    s = 0
    for e in lst:
        s += int(e)
    return s

def main():
    ret = -1

    raw = sys.stdin.read()
    rl = raw.split('\n')[1].split(' ')
    rl.sort()
    rl.reverse()
    gl = []

    for i in range(len(rl), 0, -1):
        cl = comb_gen(rl, i)
        for l in cl:
            if sum_element(l) % 3 != 0: continue
            gl.append(l)

    gl = perm_gen(gl)
    for ll in gl:
        for l in ll:
            if int(l[len(l)-1]) != 0 : continue
            ret = ''.join(l)
            ret = re.sub('^0*', '', ret)
            if len(ret) != 0:
                ret = int(ret)
            else:
                ret = 0
            break
        if ret != -1: break

    sys.stdout.write(str(ret))

if __name__ == '__main__':
    main()