#include <bits/stdc++.h>
using namespace std;
long long mod = 1000000007;
long long mod2 = 998244353;
long long mod3 = 1000003;
long long mod4 = 998244853;
long long inf = 1000000000000000000;
double pi = 2 * acos(0);
int dh[4] = {1, -1, 0, 0};
int dw[4] = {0, 0, 1, -1};
int ddh[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
int ddw[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
long long lmax(long long a, long long b) {
  if (a < b)
    return b;
  else
    return a;
}
long long lmin(long long a, long long b) {
  if (a < b)
    return a;
  else
    return b;
}
long long gcd(long long a, long long b) {
  if (a < b) swap(a, b);
  if (b == 0) return a;
  if (a % b == 0) return b;
  return gcd(b, a % b);
}
long long Pow(long long n, long long k) {
  long long ret = 1;
  long long now = n;
  while (k > 0) {
    if (k & 1) ret *= now;
    now *= now;
    k /= 2;
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int l, r;
  cin >> l >> r;
  for (long long i = l; i < r + 1; i++) {
    int cnt[10];
    fill(cnt, cnt + 10, 0);
    long long u = i;
    int c = 0;
    while (u > 0) {
      long long y = u % 10;
      if (cnt[y] == 1) {
        c = 1;
        break;
      }
      cnt[y]++;
      u /= 10;
    }
    if (c == 0) {
      cout << i << endl;
      return 0;
    }
  }
  cout << -1 << endl;
}
