1 //Author: xiaowuga
 2 #include <bits/stdc++.h>
 3 using namespace std;
 4 #define inf 0x3f3f3f3f
 5 #define MAX INT_MAX
 6 #define mem(s,ch) memset(s,ch,sizeof(s))
 7 const long long N=518;
 8 const long long mod=1e9+7;
 9 typedef long long LL;
10 typedef int II;
11 typedef unsigned long long ull;
12 #define nc cout<<"nc"<<endl
13 #define sp " "
14 ull p1=31,p2=47;
15 ull x1[N],x2[N];
16 vector<string>a;
17 II n,m;
18 ull Hash[N][N];
19 void init(){
20     x1[0]=1;x2[0]=1;
21     for(II i=1;i<501;i++){
22         x1[i]=x1[i-1]*p1;
23         x2[i]=x2[i-1]*p2;
24    }
25 }
26 void hash_init(){
27     mem(Hash,0);
28     for(II i=1;i<=n;i++){
29         for(II j=1;j<=m;j++){
30             Hash[i][j]=Hash[i][j-1]*p1+a[i-1][j-1]-'a'+1;
31         }
32     }
33     for(II j=1;j<=m;j++){
34         for(II i=1;i<=n;i++){
35             Hash[i][j]=Hash[i-1][j]*p2+Hash[i][j];
36        }
37     }
38 }
39 ull Hash_get(II x,II y,II l){
40     ull ans=Hash[x+l][y+l]-Hash[x][y+l]*x2[l];
41     ull res=Hash[x+l][y]-Hash[x][y]*x2[l];
42     return ans-res*x1[l];
43 }
44 bool OK(II k){
45     if(!k) return false;
46     unordered_set<ull>q;
47     for(II i=0;i+k<=n;i++){
48         for(II j=0;j+k<=m;j++){
49             ull ans=Hash_get(i,j,k);
50             if(q.find(ans)!=q.end()) return true;
51             else q.insert(ans);
52         }
53     }
54     return false;
55 }
56 int main() {
57     ios::sync_with_stdio(false);cin.tie(0);
58     init();
59     while(cin>>n>>m){
60         a.resize(n);
61         for(II i=0;i<n;i++) cin>>a[i];
62         hash_init();
63         II l=1,r=min(n,m)+1;
64         while(l<r){
65             II mid=l+(r-l+1)/2;
66             if(OK(mid)) l=mid;
67             else r=mid-1;
68         }
69         if(OK(l)) cout<<l<<endl;
70         else cout<<0<<endl;
71     }
72     return 0;
73 }

 1 //Author: xiaowuga
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <set>
 5 #include <vector>
 6 #include <queue>
 7 #include <cmath>
 8 #include <cstring>
 9 #include <cstdio>
10 #include <ctime>
11 #include <map>
12 #include <bitset>
13 #include <stack>
14 #include <cctype>
15 #define maxx INT_MAX
16 #define minn INT_MIN
17 #define inf 0x3f3f3f3f
18 #define mem(s,ch) memset(s,ch,sizeof(s))
19 #define nc cout<<"nc"<<endl
20 #define sp " "
21 const long long N=305;
22 const long long mod=1e9+7;
23 using namespace std;
24 typedef long long LL;
25 typedef int II;
26 II n,k;
27 vector<int>pr[N];
28 LL p[N][N]={0};
29 LL A[N];
30 void init(){
31     for(int i=0;i<=300;i++) p[i][0]=1;
32     for(int i=1;i<=300;i++)
33         for(int j=1;j<=i;j++){
34             p[i][j]=(p[i-1][j]+p[i-1][j-1])%mod;
35         }
36     A[0]=0;A[1]=1;
37     for(II i=2;i<N;i++) A[i]=A[i-1]*i%mod;
38 }
39 int main() {
40     ios::sync_with_stdio(false);cin.tie(0);
41     init();
42     while(cin>>n>>k){
43         for(II i=0;i<=n;i++) pr[i].clear();
44         for(II i=0;i<n-1;i++){
45             II x,y;cin>>x>>y;
46             pr[x].push_back(y);pr[y].push_back(x);
47         }
48         if(k==0){cout<<1<<endl;continue;}
49         LL ans=0;
50         LL li=min(n-1,k-1);
51         for(II i=0;i<=li;i++){
52             LL tmp=p[k][i+1]*A[i+1]%mod;
53             LL t=p[n-1][i]*tmp%mod;
54             ans=(ans+t)%mod;
55         }
56         cout<<ans<<endl;
57     }
58     return 0;
59 }