n = int(input())
t = [0]*3
a = [input() for i in range(n)]
a = ''.join(a).split('0')
for i in range(len(a)):
    x = max(list(map(int,a[i])))
    t[x%3] = x
if t[0] == 0 and (t[1]+t[2])%3 != 0:print('no')
elif max(t[0],t[1]+t[2])%3 == 0: print(max(t[0],t[1]+t[2]))
else:print(t[0])