s = input()
number = ''
d = {}
i = 0
while s[i] != '0':
    if s[i] in '123456789':
        if s[i] not in d.keys():
            d[s[i]] = 1
        else:
            d[s[i]] += 1
    i += 1
    
for key in d.keys():
    if d[key] % 3 == 0:
        d[key] = d[key] // 3
    else:
        number = 'NO'
        break
    
if number == 'NO':
    print(number)
else:
    for k in sorted(d.keys()):
        number += k * d[k]
    print(number * 3)