A = input()

B = input()

if (len(A) == 1 or A[0] != '0') and (len(B) == 1 or B[0] != '0'):
    
    try:
        
        A = int(A)
        
        B = int(B)
        
        print('OK')
        
    except:
        
        print('NG')
        
else:
    
    print('NG')