N, K = map(int, input().split())

if K == 1:
    if N == 1:
        print('0')
    else:
        print(-1)
elif K == 2:
    res = []
    for i in range(N):
        if (i // 2) % 2 == 0:
            res.append('0')
        else:
            res.append('1')
    print(''.join(res))
elif K % 2 == 0:
    if N < K:
        print(-1)
    else:
        half = K // 2
        first_half = '0' + '1' * (half - 1)
        palindrome = first_half + first_half[::-1]
        remaining = N - K
        if remaining > 0:
            palindrome += '1' + '0' * (remaining - 1)
        print(palindrome)
else:
    print(-1)