/* 2459 */

 #include <iostream>

 #include <sstream>

 #include <string>

 #include <map>

 #include <queue>

 #include <set>

 #include <stack>

 #include <vector>

 #include <deque>

 #include <algorithm>

 #include <cstdio>

 #include <cmath>

 #include <ctime>

 #include <cstring>

 #include <climits>

 #include <cctype>

 #include <cassert>

 #include <functional>

 #include <iterator>

 #include <iomanip>

 using namespace std;

 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>

 #define stpii            set<pair<int, int> >

 #define mpii            map<int,int>

 #define vi                vector<int>

 #define pii                pair<int,int>

 #define vpii            vector<pair<int,int> >

 #define rep(i, a, n)     for (int i=a;i<n;++i)

 #define per(i, a, n)     for (int i=n-1;i>=a;--i)

 #define clr                clear

 #define pb                 push_back

 #define mp                 make_pair

 #define fir                first

 #define sec                second

 #define all(x)             (x).begin(),(x).end()

 #define SZ(x)             ((int)(x).size())

 #define lson            l, mid, rt<<1

 #define rson            mid+1, r, rt<<1|1

 const int INF = 0x3f3f3f3f;

 const int maxn = 1e5+;

 char s[maxn];

 int a[maxn];

 int rrank[maxn], height[maxn], sa[maxn];

 int wa[maxn], wb[maxn], wc[maxn], wv[maxn];

 int dp[maxn][];

 int mx[maxn], L[maxn];

 bool cmp(int *r, int a, int b, int l) {

     return r[a]==r[b] && r[a+l]==r[b+l];

 }

 void da(int *r, int *sa, int n, int m) {

     int i, j, *x=wa, *y=wb, *t, p;

     for (i=; i<m; ++i) wc[i] = ;

     for (i=; i<n; ++i) wc[x[i]=r[i]]++;

     for (i=; i<m; ++i) wc[i] += wc[i-];

     for (i=n-; i>=; --i) sa[--wc[x[i]]] = i;

     for (j=,p=; p<n; j*=, m=p) {

         for (p=,i=n-j; i<n; ++i) y[p++] = i;

         for (i=; i<n; ++i) if (sa[i] >= j) y[p++] = sa[i] - j;

         for (i=; i<n; ++i) wv[i] = x[y[i]];

         for (i=; i<m; ++i) wc[i] = ;

         for (i=; i<n; ++i) wc[x[i]]++;

         for (i=; i<m; ++i) wc[i] += wc[i-];

         for (i=n-; i>=; --i) sa[--wc[wv[i]]] = y[i];

         for (t=x, x=y, y=t, p=, i=, x[sa[]]=; i<n; ++i)

             x[sa[i]] = cmp(y, sa[i-], sa[i], j) ? p- : p++;

     }

 }

 void calheight(int *r, int *sa, int n) {

     int i, j, k = ;

     for (i=; i<=n; ++i) rrank[sa[i]] = i;

     for (i=; i<n; height[rrank[i++]]=k)

     for (k?k--:, j=sa[rrank[i]-]; r[j+k]==r[i+k]; ++k) ;

 }

 void init_RMQ(int n) {

     int i, j;

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

         dp[i][] = height[i];

     dp[][] = INF;

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

         for (i=; i+(<<j)-<=n; ++i)

             dp[i][j] = min(dp[i][j-], dp[i+(<<(j-))][j-]);

 }

 int RMQ(int l, int r) {

     if (l > r)

         swap(l, r);

     int k = ;

     ++l;

     while (<<(k+) <= r-l+)

         ++k;

     return min(dp[l][k], dp[r-(<<k)+][k]);

 }

 void printSa(int n) {

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

         printf("%d ", sa[i]);

     putchar('\n');

 }

 void printHeight(int n) {

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

         printf("%d ", height[i]);

     putchar('\n');

 }

 void solve() {

     int n;

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

         if (s[i] == '\0') {

             n = i;

             break;

         }

         a[i] = s[i] - 'a' + ;

     }

     a[n] = ;

     da(a, sa, n+, );

     calheight(a, sa, n);

     init_RMQ(n);

     int n_ = n >> , tmp;

     rep(i, , n_) {

         mx[i] = ;

         for (int p=, q=i; q<n; p=q, q+=i) {

             tmp = RMQ(rrank[p], rrank[q]);

             mx[i] = max(mx[i], tmp/i+);

             if (tmp%i) {

                 tmp = RMQ(rrank[p-(i-tmp%i)], rrank[q-(i-tmp%i)]);

                 mx[i] = max(mx[i], tmp/i+);

             }

         }

     }

     int ans = ;

     rep(i, , n_)

         ans = max(ans, mx[i]);

     int ln = ;

     rep(i, , n_) {

         if (mx[i] == ans) {

             L[ln++] = i;

         }

     }

     int beg = , len = ;

     rep(i, , n+) {

         rep(j, , ln) {

             int p = sa[i];

             if (p+L[j] >= n)

                 continue;

             tmp = RMQ(rrank[p], rrank[p+L[j]]);

             if (tmp/L[j]+ >= ans) {

                 beg = p;

                 len = L[j] * ans;

                 goto _output;

             }

         }

     }

     _output:

     s[beg+len] = '\0';

     puts(s+beg);

 }

 int main() {

     ios::sync_with_stdio(false);

     #ifndef ONLINE_JUDGE

         freopen("data.in", "r", stdin);

         freopen("data.out", "w", stdout);

     #endif

     int t = ;

     while (scanf("%s", s)!=EOF && (s[]!='#')) {

         printf("Case %d: ", ++t);

         solve();

     }

     #ifndef ONLINE_JUDGE

         printf("time = %d.\n", (int)clock());

     #endif

     return ;

 }

 from random import randint, shuffle

 import shutil

 import string

 def GenDataIn():

     with open("data.in", "w") as fout:

         t = 20

         bound = 10**2

         lc = list(string.lowercase)

         for tt in xrange(t):

             length = randint(100, 500)

             line = ""

             for i in xrange(length):

                 idx = randint(0, 25)

                 line += lc[idx]

             fout.write("%s\n" % line)

         fout.write("#\n")

 def MovDataIn():

     desFileName = "F:\eclipse_prj\workspace\hdoj\data.in"

     shutil.copyfile("data.in", desFileName)

 if __name__ == "__main__":

     GenDataIn()

     MovDataIn()