#include <bits/stdc++.h>
using namespace std;
int main() {
  int y, l, r, x, rem;
  cin >> l >> r;
  for (x = l; x <= r; x++) {
    y = x;
    set<int> s;
    while (y != 0) {
      rem = y % 10;
      if (s.find(rem) == s.end())
        s.insert(rem);
      else
        break;
      y /= 10;
    }
    if (y == 0) break;
  }
  if (y == 0)
    cout << x;
  else
    cout << -1;
  return 0;
}
