每日，，

只粘程式碼吧，思路一片混亂，等明天想清楚了再說吧，總之就是字尾陣列+RMQ，以及字典序的判斷（=。=| wa到哭

#include<stdio.h>
#include<string.h>
#define rep(i,n) for(int i = 0;i < n; i++)
#include<iostream>
#include<math.h>
using namespace std;
char s[100010];
#define maxn 100000+10
int w[maxn],rk[maxn],sa[maxn],wa[maxn],height[maxn],res[maxn];
void getSa (int len,int up) {

	int *k = rk,*id = height,*r = res, *cnt = wa;
	rep(i,up) cnt[i] = 0;
	rep(i,len) cnt[k[i] = w[i]]++;
	rep(i,up) cnt[i+1] += cnt[i];
	for(int i = len - 1; i >= 0; i--) {
		sa[--cnt[k[i]]] = i;
	}
	//初始化
	int d = 1,p = 0;
	while(p < len){
		for(int i = len - d; i < len; i++) id[p++] = i;
		rep(i,len)	if(sa[i] >= d) id[p++] = sa[i] - d;//id儲存了按後h/2排序的的序列，即排第i的後h/2的是原陣列中的哪一個，往前d個找開頭
		rep(i,len) r[i] = k[id[i]];   //重新構造串！先對第二關鍵字排序！！！！

		rep(i,up) cnt[i] = 0;
		rep(i,len) cnt[r[i]]++;
		rep(i,up) cnt[i+1] += cnt[i];
		for(int i = len - 1; i >= 0; i--) {  //在對第一關鍵字排序！！！
			sa[--cnt[r[i]]] = id[i];
		}
		//同上

		swap(k,r);
		p = 0;
		k[sa[0]] = p++; //更新字元上限
		rep(i,len-1) {
			if(sa[i]+d < len && sa[i+1]+d <len &&r[sa[i]] == r[sa[i+1]]&& r[sa[i]+d] == r[sa[i+1]+d])
				k[sa[i+1]] = p - 1;
			else k[sa[i+1]] = p++;
		}
		//懂了！
		if(p >= len) return ; //超出len，直接結束
		d *= 2,up = p, p = 0;
	}
}
void getHeight(int len) {
	rep(i,len) rk[sa[i]] = i;
	height[0] =  0;
	for(int i = 0,p = 0; i < len - 1; i++) {
		int j = sa[rk[i]-1];
		while(i+p < len&& j+p < len&& w[i+p] == w[j+p]) {
			p++;
		}
		height[rk[i]] = p;
		p = max(0,p - 1);
	}
}
int f[maxn][21],ft[maxn];
void rmq(int n){
     int i,j;
     for (i=1;i<=n;i++)
       f[i][0]=height[i];
     for (j=1;j<20;j++)
         for (i=1;i+(1<<j)-1<=n;i++)
         f[i][j]=min(f[i][j-1],f[i+(1<<j-1)][j-1]);
     return ;
}
int lcp(int a,int b){
    int x=rk[a],y=rk[b];
    if (x>y) {int t=x; x=y; y=t;}
    x++;
    int t=ft[y-x+1];
    return min(f[x][t],f[y-(1<<t)+1][t]);
}
int shu[maxn];
int main()
{
    char xi;
    int n,up,cas=1,cn;
    for (int i=0; i<maxn; i++) ft[i]=int(double(log(i))/log(2.00));
    while(scanf("%s",s)!=EOF)
    {
        if(s[0]=='#') break;
        xi='z'+1;
        n=strlen(s);
        up=0;
        for(int i=0;i<n;i++)
        {
            w[i]=s[i];
            up=max(up,w[i]);
            if(s[i]<xi) xi=s[i];
        }
        w[n]=0;
        getSa(n+1,200);
        getHeight(n+1);
        rmq(n);

       int tmp,ans=0,rr=0,tt,ll=0,st,sst;
        for(int l=1; l<n; l++)
             for(int i=0; i+l<n; i+=l)
            {
                st=i;
                tmp=lcp(i,i+l);
                rr=tmp/l+1;
                tt=i-(l-tmp%l);
                if (tt>=0&&tmp%l!=0)
                    if (lcp(tt,tt+l)>=tmp)
                    {
                        rr=lcp(tt,tt+l)/l+1;
                        st=tt;
                    }
                   // printf("rr==%d\n",i);
                   if(rr>ans)
                    {
                        ans=rr;
                      //  printf("i==%d ans==%d  tmp==%d\n",i,ans,tmp);
                        cn=0;
                        shu[cn++]=l;
                    }
                    if(rr==ans)
                {

                    shu[cn++]=l;
                }


            }
            int b=0,c;
        for(int i=1;i<=n&&!b;i++){  
            for(int j=0;j<cn;j++){
                int tl=shu[j];
                if(lcp(sa[i],sa[i]+tl)>=(ans-1)*tl){
                    st=sa[i];
                    ll=tl*ans;
                    b=1;
                    break;
                }
            }
        }
        printf("Case %d: ",cas++);
            if(ans>1){
        for(int i=st;i<st+ll;i++)
            printf("%c",s[i]);
        printf("\n");
            }
            else
                printf("%c\n",xi);
    }
    return 0;
}