#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
#define CRP(t, x) const t &x
#define OPL(t, x) bool operator<(CRP(t, x)) const
#define FIL(x, v) memset(x, v, sizeof(x))
#define CLR(x) FIL(x, 0)
#define NE1(x) FIL(x, -1)
#define INF(x) FIL(x, 0x3f)
#ifndef _DEBUG
#define _DEBUG 0
#endif // !_DEBUG
#define IFD if (_DEBUG)
typedef long long ll, i64;
int main()
{
    int l, r;
    scanf("%d%d", &l, &r);
    for (int i = l; i <= r; i++)
    {
        char s[20];
        sprintf(s, "%d", i);
        bool flag = true;
        for (int i = 0; s[i]; i++)
            for (int j = 0; j < i; j++)
                if (s[j] == s[i]) flag = false;
        if (flag) return puts(s), 0;
    }
    puts("-1");
    return 0;
}