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] = max(dp[i+1][j], max(dp[i][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 <iostream>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <iterator>
#include <queue>
#include <stack>
#include <deque>
#include <sstream>
#include <algorithm>
#include <numeric>
#include <string>
#include <cmath>
#include <complex>
#include <functional>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cstdlib>
#include <cctype>

#define REP(i,m,n) for(int i=m;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define rp(i,c) rep(i,(int)c.size())
#define fr(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)
#define mp make_pair
#define pb push_back
#define all(c) (c).begin(),(c).end()
#define rall(u) (u).rbegin(),(u).rend()
#define dbg(x) cerr<<#x<<" = "<<(x)<<endl
#define v_delete(a,b) (a).erase(remove((a).begin(), (a).end(), b), (a).end())
#define v_unique(a) (a).erase(unique((a).begin(), (a).end()), (a).end())
#define VV(T) vector<vector< T > >
#define init(a,b) memset((a), (b), sizeof((a)))

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
const int inf=1<<28;
const double EPS=1e-9;
const long long INF = 100001000010000100ll;

template<class T>int SIZE(T a){return a.size();}
template<class T>string IntToString(T num){string res;stringstream ss;ss<<num;return ss.str();}
template<class T>T StringToInt(string str){T res=0;for(int i=0;i<SIZE(str);i++)res=(res*10+str[i]-'0');return res;}
template<class T>T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);}
template<class T>T lcm(T a,T b){return a/gcd(a,b)*b;}

template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T> void input(T* a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
typedef pair<int,int> pii;


string L, R;

int dp[4000+10][4000+10];

int main(){
	while(cin >> L >> R){
		memset(dp, 0, sizeof(dp));
		int ans=0;
		rp(i, R){
			rp(j, L){
				if(R[i]==L[j]){
					dp[i][j] = dp[i-1][j-1] + 1;
				}else{
					dp[i][j]=0;
				}
				ans=max(ans, dp[i][j]);
			}
		}
		cout << ans << endl;
	}

	return 0;

}

C++: #include<bits/stdc++.h>
using namespace std;
short cnt[4100][4100];
int main(){
  string str1,str2;
  while(cin >> str1){
    cin >> str2;
    int len1 = str1.size();
    int len2 = str2.size();
    str1 = ' ' + str1;
    str2 = ' ' + str2;
    for(int i=1;i<=len1;i++){
      cnt[i][0] = 0;
    } 
    for(int i=1;i<=len2;i++){
      cnt[0][i] = 0;
    }
    int ret = 0;
    for(int i=1;i<=len1;i++){
      for(int j=1;j<=len2;j++){
	if(str1[i] == str2[j]){
	  cnt[i][j] = cnt[i-1][j-1] + 1;
	}
	else {
	  cnt[i][j] = 0;
	}
	ret = max(ret,cnt[i][j]);
      }
    }
    cout << ret << endl;
  }	
}

C++: #include <iostream>
using namespace std;

int main(){
	string a,b;
	while(cin >> a >> b){
		int ans = 0;
		for(int x = 0 ; x < 2 ; x++){
			for(int i = 0 ; i < a.size() ; i++){
				int len = 0;
				for(int j = 0 ; j < b.size() ; j++){
					if(i+len < a.size() && a[i+len] == b[j])len++;
					else len = a[i] == b[j];
					ans = max(len,ans);
				}
			}
			swap(a,b);
		}

		cout << ans << endl;
	}
}
// a b c d e
// abcdef
// def

C++: #include<bits/stdc++.h>
#pragma warning(disable:4996)
using namespace std;
using ll = long long;
const int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
int main() {
	string s, t;
	while (cin >> s >> t) {
		int s_size = s.size();
		int t_size = t.size();
		int ans = 0;

		for (int i = 0; i < s.size(); i++) {//sをずらしていく
			vector<int>a0(t.size());
			for (int j = 0; j < t.size(); j++) {
				if (j < t.size() && j + i < s.size() && t[j] == s[j + i]) {
					a0[j]++;
				}
				else if (j < t.size() && j + i < s.size() && t[j] != s[j + i]) {
					continue;
				}
			}
			int nagasa = 0;
			int x = 0;
			for (int i = 0; i < t.size(); i++) {
				int nagasa2 = 0;
				x = i;
				while (x < a0.size() && a0[x] == 1) {
					x++;
					nagasa2++;
				}
				nagasa = max(nagasa, nagasa2);
			}
			ans = max(ans, nagasa);
		}

		for (int i = 0; i < t.size(); i++) {//tをずらしていく
			vector<int>a0(s.size());

			for (int j = 0; j < s.size(); j++) {
				if (j < s.size() && j + i < t.size() && s[j] == t[j + i]) {
					a0[j]++;
				}
				else if (j < s.size() && j + i < t.size() && s[j] != t[j + i]) {
					continue;
				}
			}
			int nagasa = 0;
			int x = 0;
			for (int i = 0; i < t.size(); i++) {
				int nagasa2 = 0;
				x = i;
				while (x < a0.size() && a0[x] == 1) {
					x++;
					nagasa2++;
				}
				nagasa = max(nagasa, nagasa2);
			}
			ans = max(ans, nagasa);
		}
		cout << ans << endl;
	}
}

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, save=0, ans = 0;
		cin>>s;
		cin>>t;
		if(s==""){
		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= 0;
				while (1){
					if (s[i + roop1] == 0 || t[j + roop1] == 0){
						break;
					}
					else{
						if (s[i + roop1] == t[j + roop1]){
							save += 1;
							roop1++;
						}
					else if (s[i + roop1] != t[j + roop1]){
							ans=max(ans,save);
							break;
						}
					}
				}
			}
		}
	}
	cout<<ans<<endl;
	}
	
	return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
    string s, t; int roop1, roop2 = 0, save[10000], ans = 0;
    cin >> s >> t;
    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;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
 
int solve(string s, string t){
    int ans = 0;
    for(int i=0 ; i < s.size() ; i++ ){
        string s_ = s.substr(i);
        int len = min( s_.size() , t.size() );
        int a[4001] = {0};
         
        for(int j=0 ; j < len ; j++ ){
            if( s_[j] == t[j] ) a[j] = 1;
        }
         
        int sum=0;
        for(int j=1 ; j < len ; j++ ){
            if( a[j-1] > 0 && a[j] > 0 ){
                a[j] = a[j-1] + 1;
                sum = max( sum , a[j-1] + 1 );
            }
        }
        ans = max( ans , sum );
    }
    return ans;
}
 
int main(){
    string s, t;
    while( cin >> s >> t ){
        int ans = max( solve(s,t) , solve(t,s) );
        cout << ans << endl;
    }
}