Go: ///
// File:  0528.go
// Author: ymiyamoto
//
// Created on Thu Mar 22 01:52:09 2018
//
package main

import (
	"bufio"
	"fmt"
	"os"
)

var S, T string
var dp [4001][4001]int

func max(a, b int) int {
	if a < b {
		return b
	}
	return a
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	for {
		scanner.Scan()
		S = scanner.Text()
		if len(S) == 0 {
			return
		}

		scanner.Scan()
		T = scanner.Text()

		for i := range dp {
			for j := range dp[i] {
				dp[i][j] = 0
			}
		}

		dp[0][0] = 0
		for i := range S {
			for j := range T {
				if S[i] == T[j] {
					dp[i+1][j+1] = dp[i][j] + 1
				} else {
					dp[i+1][j+1] = 0
				}
			}
		}

		var m int
		for i := range dp {
			for j := range dp[i] {
				m = max(m, dp[i][j])
			}
		}
		fmt.Println(m)
	}
}

C++: #include<bits/stdc++.h>
using namespace std;
int ans,s1,s2;
int solve(string text,string patn,int tt,int pp);
string text,patn;

int main(){

    while(cin >> text){
        cin >> patn;
        s1=text.size();
        s2=0;
        while(s1!=0 || s2<=patn.size()){
            if(s1!=0)s1--;
            else s2++;
            ans=max(ans,solve(text,patn,s1,s2));
            }
        cout << ans << endl;
        ans=0;
    }
    return 0;
}

int solve(string text,string patn,int tl,int pl){
    int tt=0;
    int pp=0;
    int len=min(text.size()-tl,patn.size()-pl);
    for(int i=0;i<len;i++){
        if(text[tl+i]==patn[pl+i]){
            tt++;
        }else{
            pp=(pp,tt);
            tt=0;
        }
    }
    return max(pp,tt);
}

C++: #include <string>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
class SuffixArray {
	void CEB(vector<int> &v, vector<int> &b) {
		int vs = v.size(), bs = b.size();
		fill(b.begin(), b.end(), 0);
		for (int i = 0; i < vs; i++) b[v[i]]++;
		for (int i = 1; i < bs; i++) b[i] += b[i - 1];
	}
	void ISort(vector<int> &v, vector<int> &SA, int mv, vector<int> &b, vector<int> &isL) {
		int vs = v.size(), bs = b.size();
		fill(b.begin(), b.end(), 0);
		for (int i = 0; i < vs; i++) b[v[i]]++;
		int sum = 0;
		for (int i = 0; i < bs; i++) b[i] += sum, swap(sum, b[i]);
		for (int i = 0; i < vs; i++) {
			if (SA[i] > 0 && isL[SA[i] - 1]) SA[b[v[SA[i] - 1]]++] = SA[i] - 1;
		}
	}
	void IISort(vector<int> &v, vector<int> &SA, int mv, vector<int> &b, vector<int> &isL) {
		CEB(v, b);
		for (int i = v.size() - 1; i >= 0; i--) {
			if (SA[i] > 0 && !isL[SA[i] - 1]) SA[--b[v[SA[i] - 1]]] = SA[i] - 1;
		}
	}
	vector<int>SA_IS(vector<int> v, int mv) {
		int vs = v.size();
		if (vs == 1) return vector<int>(1, 0);
		vector<int> isL(vs), b(mv + 1), SA(vs, -1), ord(vs);
		auto isLMS = [&](int x)->bool { return x > 0 && isL[x - 1] && !isL[x]; };
		for (int i = vs - 2; i >= 0; i--) isL[i] = (v[i] > v[i + 1]) || (v[i] == v[i + 1] && isL[i + 1]);
		CEB(v, b);
		for (int i = 0; i < vs; i++) {
			if (isLMS(i)) SA[--b[v[i]]] = i;
		}
		ISort(v, SA, mv, b, isL);
		IISort(v, SA, mv, b, isL);
		int cur = 0;
		for (int i = 0; i < vs; i++) {
			if (isLMS(i)) ord[i] = cur++;
		}
		vector<int> nxv(cur);
		cur = -1;
		int prev = -1;
		for (int i = 0; i < vs; i++) {
			if (!isLMS(SA[i])) continue;
			bool diff = false;
			for (int d = 0; d < vs; d++) {
				if (prev == -1 || v[SA[i] + d] != v[prev + d] || isL[SA[i] + d] != isL[prev + d]) {
					diff = true;
					break;
				}
				else if (d && isLMS(SA[i] + d))break;
			}
			if (diff) cur++, prev = SA[i];
			nxv[ord[SA[i]]] = cur;
		}
		vector<int> reord(nxv.size());
		for (int i = 0; i < vs; i++) {
			if (isLMS(i)) reord[ord[i]] = i;
		}
		vector<int> nxSA = SA_IS(nxv, cur);
		CEB(v, b);
		for (int i = 0; i < SA.size(); i++) SA[i] = -1;
		for (int i = nxSA.size() - 1; i >= 0; i--) {
			SA[--b[v[reord[nxSA[i]]]]] = reord[nxSA[i]];
		}
		ISort(v, SA, mv, b, isL);
		IISort(v, SA, mv, b, isL);
		return SA;
	}
	vector<int>SA_IS(string s) {
		vector<int> v(s.size() + 1);
		for (int i = 0; i < s.size(); i++) v[i] = s[i] + 1;
		return SA_IS(v, *max_element(v.begin(), v.end()));
	}
	vector<int>construct_lcp(string &s, vector<int> &sa) {
		vector<int> lcp(s.size()), rank(s.size() + 1);
		int n = s.size(), h = 0;
		for (int i = 0; i <= n; i++) rank[sa[i]] = i;
		for (int i = 0; i < n; i++) {
			int j = sa[rank[i] - 1];
			if (h) h--;
			for (; j + h < n && i + h < n; h++) {
				if (s[j + h] != s[i + h]) break;
			}
			lcp[rank[i] - 1] = h;
		}
		return lcp;
	}
public:
	string s;
	vector<int> sa, lcp;
	void init(string &T) {
		s = T;
		sa = SA_IS(s);
		lcp = construct_lcp(s, sa);
	}
	SuffixArray(string &t) { init(t); }
	SuffixArray() {}
	bool contain(string &t) {
		int a = 0, b = s.size();
		while (b - a > 1) {
			int c = (a + b) / 2;
			if (s.compare(sa[c], t.size(), t) < 0) a = c;
			else b = c;
		}
		return s.compare(sa[b], t.size(), t) == 0;
	}
};
string s, t;
int main() {
	while(cin >> s >> t) {
		int sl = s.size(); s += '$' + t;
		SuffixArray v(s);
		int ret = 0, e = s.size();
		for(int i = 0; i < e; i++) {
			if((v.sa[i] < sl) != (v.sa[i + 1] < sl)) ret = max(ret, v.lcp[i]);
		}
		cout << ret << endl;
	}
}

C++: #include<bits/stdc++.h>

#define int long long int
#define rep(a,b,c) for(int a=b;a<c;a++)
#define repm(a,b,c) for(int a=(b-1);a>=c;a--)
#define pb push_back
#define str string
#define sf(a) scanfs("%d",&a)
#define pb push_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) (v).begin(), (v).end()

using namespace std;

const int INF = 1e18 + 9;
const int Mod = 1e9 + 7;
inline int replac(str s){double ans=0;rep(i,0,s.length()){ans+=(s[i]-'0')*pow(10,s.length()-i-1);}return (int)ans;}
inline string numstr(int m){str s="";while(m>0){char c;int a=m/10;if(a>0)a=m%(a*10);else a=m;c=(char)('0'+a);s+=c;m/=10;}str st="";for(int i=s.size()-1;i>=0;i--){st+=s[i];}return st;}
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef vector<pii> vii;
int dp[4005][4005];
signed main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    str n,m;
    while(cin >> n){
    rep(i,0,4000)rep(j,0,4000)dp[i][j]=0;
    cin >> m;
    rep(i,0,n.size()){
        rep(j,0,m.size()){
            if(n[i]==m[j]&&i>0&&j>0){
                dp[i][j]=max(dp[i-1][j-1]+1,dp[i][j]);
            }else if(n[i]==m[j]){
                dp[i][j]=1;
            }else{
                dp[i][j]=max(dp[i][j-1],dp[i][j]);
            }
        }
    }int ans=0;
    rep(i,0,n.size()){
        ans=max(ans,dp[i][m.size()-1]);
    }
    cout << ans << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
string a,b;
int c,d;
int dp[2][5000],ans;
int main(){
  while(cin>>a>>b){
    c=a.size(),d=b.size();
    ans=0;
    dp[0][0]=dp[1][0]=0;
    for(int i=1;i<=c;i++){
      for(int j=1;j<=d;j++){
	int ni=i%2,ri=1-i%2;
	if(a[i-1]==b[j-1]){
	  dp[ni][j]=dp[ri][j-1]+1;
	}else{
	  dp[ni][j]=0;
	}
	ans=max(ans,dp[ni][j]);
      }
    }
    cout<<ans<<endl;
  }
  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<string>
#define rep(i,s,n) for(int i=s;i<n;i++)
using namespace std;
int dp[4001][4001];
int main(){
	string a,b;
	while(cin>>a>>b){
	int h=a.size()+1,w=b.size()+1,ans=0;
	rep(i,0,h)rep(j,0,w)dp[i][j]=0;
	rep(i,1,h)rep(j,1,w)if(a[i-1]==b[j-1])dp[i][j]=dp[i-1][j-1]+1,ans=max(ans,dp[i][j]);
	cout<<ans<<endl;
	}
	return 0;
}

C++: //JOI 0528 Common Sub-String
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
	while(1){
		string s, t; int roop1=0, roop2 = 0, save[6400000]={}, ans = 0;
		cin>>s;
		cin>>t;
		if(cin.eof())
		break;
	for (int i = 0; i<s.size(); i++){
		for (int j = 0; j<t.size(); j++){
			if (s[i] == t[j]){
				roop1 = 0;
				save[roop2] = 0;
				while (1){
					if (s[i + roop1] == 0 || t[j + roop1] == 0){
						break;
					}
					else{
						if (s[i + roop1] == t[j + roop1]){
							save[roop2] += 1;
							roop1++;
						}
						else if (s[i + roop1] != t[j + roop1]){
							roop2++;
							break;
						}
					}
				}
			}
		}
	}
	sort(save, save + roop2 + 1);
	ans = save[roop2];
	cout << ans << endl;
	}
	return 0;
}