def fun1(a):
    arr = []
    while a>0:
        t = a % 10
        a = int(a / 10)
        arr.append(t)
    return arr
def fun2(a):
    n = len(a) - 1
    s = 0
    for i in a:
        s += i*(10**n)
        n -= 1
    return s

def resverse(a ,b):
    arr, brr = [], []
    arrv = fun1(a)
    brrv = fun1(b)
    s1 = fun2(arrv)
    s2 = fun2(brrv)
    s = s1 + s2
    srrv = fun1(a+b)
    sv = fun2(srrv)
    if sv == s:
        print(a+b)
    else:
        print('NO')



while True:
    #p = [1, 2,3]
    try:
        a, b = map(int, input().split())
        #print(a)
        #print(fun1(a))
        resverse(a, b)
    except:
        break