#include <bits/stdc++.h>
using namespace std;
int n, m, a[2000000 + 100];
int main() {
  cin >> n >> m;
  if ((m < n - 1) || (m > 2 * (n + 1))) {
    cout << -1 << endl;
    return 0;
  }
  for (int i = 1; i <= n; i++) a[2 * i] = 0;
  for (int i = 2; i <= n; i++) a[2 * i - 1] = 1;
  m = m - (n - 1);
  for (int i = 2; i <= n; i++) {
    if (m == 0) break;
    a[2 * i - 1] = 11, m--;
  }
  if (m == 1) cout << 1;
  if (m == 2) cout << 11;
  if (m == 3) cout << 11;
  if (m == 4) cout << 11;
  for (int i = 2; i <= 2 * n; i++) cout << a[i];
  if (m == 3) cout << 1;
  if (m == 4) cout << 11;
  return 0;
}
