a=input()
b=input()
if 2<=len(a) and a[0]=="0":
    print("NG")
elif 2<=len(b) and b[0]=="0":
    print("NG")
elif a.isdigit() and b.isdigit():
    a_i=int(a)
    b_i=int(b)
    print(a_i+b_i)
else:
    print("NG")