A = input()
B = input()

sort_a = sorted(A)
sort_b = sorted(B)

if A == B:
    print('OK')
elif len(A) == len(B):
    for a, b in zip(sort_a, sort_b):
        if a != b:
            print('NO')
            break
    else:
        print('OK')
else:
    print('NO')