#include <set>

 #include <map>

 #include <stack>

 #include <queue>

 #include <cmath>

 #include <ctime>

 #include <cstdio>

 #include <string>

 #include <vector>

 #include <cstring>

 #include <iostream>

 #include <algorithm>

 #include <unordered_map>

 #define  pi    acos(-1.0)

 #define  eps   1e-9

 #define  fi    first

 #define  se    second

 #define  rtl   rt<<1

 #define  rtr   rt<<1|1

 #define  bug                printf("******\n")

 #define  mem(a, b)          memset(a,b,sizeof(a))

 #define  name2str(x)        #x

 #define  fuck(x)            cout<<#x" = "<<x<<endl

 #define  sfi(a)             scanf("%d", &a)

 #define  sffi(a, b)         scanf("%d %d", &a, &b)

 #define  sfffi(a, b, c)     scanf("%d %d %d", &a, &b, &c)

 #define  sffffi(a, b, c, d) scanf("%d %d %d %d", &a, &b, &c, &d)

 #define  sfL(a)             scanf("%lld", &a)

 #define  sffL(a, b)         scanf("%lld %lld", &a, &b)

 #define  sfffL(a, b, c)     scanf("%lld %lld %lld", &a, &b, &c)

 #define  sffffL(a, b, c, d) scanf("%lld %lld %lld %lld", &a, &b, &c, &d)

 #define  sfs(a)             scanf("%s", a)

 #define  sffs(a, b)         scanf("%s %s", a, b)

 #define  sfffs(a, b, c)     scanf("%s %s %s", a, b, c)

 #define  sffffs(a, b, c, d) scanf("%s %s %s %s", a, b,c, d)

 #define  FIN                freopen("../in.txt","r",stdin)

 #define  gcd(a, b)          __gcd(a,b)

 #define  lowbit(x)          x&-x

 #define  IO                 iOS::sync_with_stdio(false)

 using namespace std;

 typedef long long LL;

 typedef unsigned long long ULL;

 const ULL seed = ;

 const LL INFLL = 0x3f3f3f3f3f3f3f3fLL;

 const int maxm = 8e6 + ;

 const int INF = 0x3f3f3f3f;

 const int mod = 1e9 + ;

 const int maxn = ;

 char s[maxn];

 int Q;

 struct Suffix_Automaton {

     int last, tot, nxt[maxn << ][], fail[maxn << ];//last是未加入此字符前最长的前缀（整个串）所属的节点的编号

     int len[maxn << ];// 最长子串的长度 (该节点子串数量 = len[x] - len[fa[x]])

     int sa[maxn << ], c[maxn << ];

     int sz[maxn << ];// 被后缀链接的个数，方便求节点字符串的个数

     LL num[maxn << ];// 该状态子串的数量

     LL maxx[maxn << ];// 长度为x的子串出现次数最多的子串的数目

     LL sum[maxn << ];// 该节点后面所形成的自字符串的总数

     LL subnum, sublen;// subnum表示不同字符串数目,sublen表示不同字符串总长度

     int X[maxn << ], Y[maxn << ]; // Y表示排名为x的节点，X表示该长度前面还有多少个

     int minn[maxn << ], mx[maxn << ];//minn[i]表示多个串在后缀自动机i节点最长公共子串，mx[i]表示单个串的最长公共子串

     void init() {

         tot = last = ;

         fail[] = len[] = ;

         for (int i = ; i < ; i++) nxt[][i] = ;

     }

     void extend(int c) {

         int u = ++tot, v = last;

         len[u] = len[v] + ;

         num[u] = ;

         for (; v && !nxt[v][c]; v = fail[v]) nxt[v][c] = u;

         if (!v) fail[u] = , sz[]++;

         else if (len[nxt[v][c]] == len[v] + ) fail[u] = nxt[v][c], sz[nxt[v][c]]++;

         else {

             int now = ++tot, cur = nxt[v][c];

             len[now] = len[v] + ;

             memcpy(nxt[now], nxt[cur], sizeof(nxt[cur]));

             fail[now] = fail[cur];

             fail[cur] = fail[u] = now;

             for (; v && nxt[v][c] == cur; v = fail[v]) nxt[v][c] = now;

             sz[now] += ;

         }

         last = u;

         //return len[last] - len[fail[last]];//多添加一个子串所产生不同子串的个数

     }

     void get_num() {// 每个节点子串出现的次数

         for (int i = ; i <= tot; i++) X[len[i]]++;

         for (int i = ; i <= tot; i++) X[i] += X[i - ];

         for (int i = ; i <= tot; i++) Y[X[len[i]]--] = i;

         for (int i = tot; i >= ; i--) num[fail[Y[i]]] += num[Y[i]];

     }

     void get_maxx(int n) {// 长度为x的子串出现次数最多的子串的数目

         get_num();

         for (int i = ; i <= tot; i++) maxx[len[i]] = max(maxx[len[i]], num[i]);

     }

     void get_sum() {// 该节点后面所形成的自字符串的总数

         get_num();

         for (int i = tot; i >= ; i--) {

             sum[Y[i]] = ;

             for (int j = ; j <= ; j++)

                 sum[Y[i]] += sum[nxt[Y[i]][j]];

         }

     }

     void get_subnum() {//本质不同的子串的个数

         subnum = ;

         for (int i = ; i <= tot; i++) subnum += len[i] - len[fail[i]];

     }

     void get_sublen() {//本质不同的子串的总长度

         sublen = ;

         for (int i = ; i <= tot; i++) sublen += 1LL * (len[i] + len[fail[i]] + ) * (len[i] - len[fail[i]]) / ;

     }

     void get_sa() { //获取sa数组

         for (int i = ; i <= tot; i++) c[len[i]]++;

         for (int i = ; i <= tot; i++) c[i] += c[i - ];

         for (int i = tot; i >= ; i--) sa[c[len[i]]--] = i;

     }

     int cntnum[maxn << ];

     void match() {//多个串的最长公共子串

         mem(cntnum, );

         int n = strlen(s), p = , ans = INF;

         for (int i = ; i < n; i++) {

             int c = s[i] - 'a';

             if (nxt[p][c]) p = nxt[p][c];

             else {

                 for (; p && !nxt[p][c]; p = fail[p]);

                 if (!p) p = ;

                 else p = nxt[p][c];

             }

             cntnum[p]++;

         }

         for (int i = tot; i; i--) cntnum[fail[Y[i]]] += cntnum[Y[i]];

         for (int i = ; i <= tot; i++)

             if (num[i] ==  && cntnum[i] == ) ans = min(ans, len[fail[i]] + );

         if (ans == INF) printf("-1\n");

         else printf("%d\n", ans);

     }

     void get_kth(int k) {//求出字典序第K的子串

         int pos = , cnt;

         string s = "";

         while (k) {

             for (int i = ; i <= ; i++) {

                 if (nxt[pos][i] && k) {

                     cnt = nxt[pos][i];

                     if (sum[cnt] < k) k -= sum[cnt];

                     else {

                         k--;

                         pos = cnt;

                         s += (char) (i + 'a');

                         break;

                     }

                 }

             }

         }

         cout << s << endl;

     }

 } sam;

 int main() {

 #ifndef ONLINE_JUDGE

     FIN;

 #endif

     sam.init();

     sfs(s + );

     int n = strlen(s + );

     for (int i = ; i <= n; i++) sam.extend((s[i] - 'a'));

     sfs(s);

     sam.get_num();

     sam.match();

 #ifndef ONLINE_JUDGE

     cout << "Totle Time : " << (double) clock() / CLOCKS_PER_SEC << "s" << endl;

 #endif

     return ;

 }