n, k = map(int, input().split())

if k == 1:
    if n == 1:
        print('0')
    elif n == 2:
        print('01')
    else:
        print(-1)
else:
    if k < (n // 2 + 1):
        print(-1)
    else:
        if k % 2 == 0:
            half = k // 2
            first_half = '0' * (half - 1) + '1'
            second_half = first_half[::-1]
            palindrome = first_half + second_half
        else:
            middle = '0'
            half = (k - 1) // 2
            first_half = '1' * half
            second_half = first_half[::-1]
            palindrome = first_half + middle + second_half
        
        remaining = n - k
        if remaining > 0:
            if palindrome[0] == '0':
                next_char = '1'
            else:
                next_char = '0'
            s = palindrome + next_char + '0' * (remaining - 1)
        else:
            s = palindrome
        print(s)