#include <iostream>

using namespace std;

int main()
{
	int A, B;
	cin >> A >> B;

	if (B * 9 < A)
	{
		cout << "-1";
		return 0;
	}

	int min_number = 0, max_number = 0;
	for (int i = 0; i < B; i++)
	{
		int tmp;
		if (A >= 9)
			tmp = 9;
		else
			tmp = A;

		A -= tmp;

		max_number = max_number * 10 + tmp;
		min_number = tmp * pow(10, i) + min_number;
	}

	cout << max_number - min_number;
}