a = input()
b = input()

for i in a:
    if i.isdigit() != True:
        print('NG')
        exit()

for i in b:
    if i.isdigit() != True:
        print('NG')
        exit()

A = int(a)
B = int(b)

if len(a) != len(str(A)):
    print('NG')
    exit()

if len(b) != len(str(B)):
    print('NG')
    exit()

print(A + B)