#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int MAXW = 1e5 + 1;
string next(string x) {
  int start = x.length() - 1, c = 0;
  bool four = false;
  for (int i = start; i >= 0; i--) {
    if (x[i] == '4') {
      four = true;
      x[i] = '7';
      for (int j = i + 1; j <= start; j++) {
        x[j] = '4';
      }
      break;
    }
  }
  if (!four) {
    x = "";
    for (int i = 0; i <= start + 1; i++) {
      x += '4';
    }
  }
  return x;
}
int main() {
  bool readfromfile = false;
  if (!readfromfile) {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
  } else {
    freopen("input.txt", "r", stdin);
  }
  long long n, m;
  cin >> n >> m;
  if (n > m + 1) {
    cout << -1 << endl;
    return 0;
  }
  if (n >= m) {
    if (n > m) {
      cout << 0;
      n--;
    }
    while (n > 0) {
      cout << 10;
      n--;
    }
  } else {
    int temp = m - n;
    string ans = "";
    while (n > 0) {
      if (temp > 0) {
        ans += '1';
        temp--;
      }
      ans += "10";
      n--;
    }
    if (temp > 2)
      cout << -1;
    else {
      while (temp > 0) {
        ans += '1';
        temp--;
      }
      cout << ans;
    }
  }
  cout << endl;
  return 0;
}
