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 <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<(int)n;i++)
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define rrep(i,n) for(int i = 1; i <= n; i++)
#define drep(i,n) for(int i = n; i >= 0; 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> pii;
const int inf=1<<28;
const double INF=1e10,EPS=1e-9;


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]; }


int main(){
	string a,b;
	while(cin >> a >> b){
		int dp[4002][4002]={0};
	int as=a.size();
	a+='a';
	int bs=b.size();
	b+='b';
	int ans=0;
	for(int i=0;i<as;i++){
		for(int j=0;j<bs;j++){
			if(a[i+1]==b[j+1]){
				dp[i+1][j+1]=dp[i][j]+1;
			}else{
				dp[i+1][j+1]=0;
			}/*
			if(dp[i+1][j+1]){
				cout << dp[i+1][j+1]<<endl;
				cout << i << "," << j << endl;
			}*/
			ans=max(ans,dp[i+1][j+1]);
		}
	}
	cout << ans << endl;
	}
	return 0;
}

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


int main(){
    string a, b;
    while (cin >> a >> b){
	if (a.size() > b.size()) swap(a, b);
	int max = 0;
	for (int index = 0; index < a.size()-1; index++){
	    for (int size = a.size(); size >= 1; size--){
		string s = a.substr(index, size);
		if (b.find(s) != -1 && max < s.size()) max = s.size();
	    }
	}
	cout << max << 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, roop2 = 0, save[100000]={}, 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;
}

C++: //#include"bits/stdc++.h"
#include<iostream>
#include<ostream>
#include<vector>
#include<string>
#include<algorithm>

#define FOR(i,a,b) for (ll i=(a),__last_##i=(b);i<__last_##i;i++)
#define RFOR(i,a,b) for (ll i=(b)-1,__last_##i=(a);i>=__last_##i;i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)


using namespace std;
using ll = long long;

void solve();

int main() {

   solve();
   return 0;

}

void solve() {

	string s, t;
	
	while (cin >> s >> t) {
		ll ans=0;
		vector<vector<ll>> dp;
		dp.resize(s.size()+1);
		REP(i, dp.size()) {
			dp[i].resize(t.size()+1);
			REP(j, dp[i].size()) {
				dp[i][j] = 0;
			}
		}
		REP(i, s.size()) {
			REP(j, t.size()) {
				if (s[i] == t[j]) {
					dp[i + 1][j + 1] = dp[i][j] + 1;
					//cout << "match" << endl;
				}
				else {
					ans = max(ans, dp[i][j]);
				}
			}
		}
		ans = max(ans, dp[s.size()][t.size()]);
		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, roop2 = 0, save[1]={}, 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]){
							ans=max(ans,save[roop2]);
							break;
						}
					}
				}
			}
		}
	}
	cout<<ans<<endl;
	}
	
	return 0;
}

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

int dp[4005][4005];

int main() {
	string s;
	while (cin >> s) {
		string sa;
		cin >> sa;
		for (int i = 0; i < 4003; i++)
			for (int j = 0; j < 4003; j++)dp[i][j] = 0;
		s.push_back('@');
		int ans = 0;
		for (int i = 0; i < s.size(); i++) {
			for (int j = 0; j < sa.size(); j++) {
				int a = s.size();

				if (s[i] == sa[j]) {
				dp[i+1][j + 1] = dp[i][j] + 1;
					ans = max(ans, dp[i+1][j + 1]);
				}
				else {
				dp[i+1][j + 1] = 0;
				}
			}
		}
		cout << ans << endl;
	}
	return 0;
}

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

int dp[4000][4000];

int main()
{
  string a, b;
  int ans = 0;
  while(cin >> a >> b)
  {
    for(int i = 0; i < a.length(); i++)
    {
      for(int j = 0; j < b.length(); j++)
      {
        if(a[i + 1] == b[j + 1])
          ans = max(dp[i + 1][j + 1] = dp[i][j] + 1, ans);
        else
          dp[i + 1][j + 1] = 0;
      }
    }
    
    cout << ans << endl;
  }
}