Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		n := io.NextInt()
		if n == 0 {
			break
		}
		accum := make([]int, 86401)
		for i := 0; i < n; i++ {
			s, e := io.Next(), io.Next()
			hs, _ := strconv.Atoi(s[:2])
			ms, _ := strconv.Atoi(s[3:5])
			ss, _ := strconv.Atoi(s[6:8])
			accum[hs*60*60+ms*60+ss]++
			he, _ := strconv.Atoi(e[:2])
			me, _ := strconv.Atoi(e[3:5])
			se, _ := strconv.Atoi(e[6:8])
			accum[he*60*60+me*60+se]--
		}
		ans := 0
		for i := 1; i < 86401; i++ {
			accum[i] += accum[i-1]
			ans = intMax(accum[i], ans)
		}
		io.Println(ans)
	}
}

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

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <vector>
#include <iostream>
#include <utility>
#include <algorithm>
#include <string>
#include <deque>
#include <queue>
#include <tuple>
#include <queue>
#include <functional>
#include <cmath>
#include <iomanip>
#include <map>
#include <set>
#include <numeric>
#include <unordered_map>
#include <unordered_set>
#include <complex>
#include <iterator>
#include <array>
#include <memory>
#include <stack>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define loop(i,s,n) for(int i=s;i<n;i++)
#define all(in) in.begin(), in.end()
template<class T, class S> void cmin(T &a, const S &b) { if (a > b)a = b; }
template<class T, class S> void cmax(T &a, const S &b) { if (a < b)a = b; }
#define MAX 9999999
using namespace std;
typedef pair<int, int> pii;
typedef pair<double,double>pdd;
typedef pair<ll,ll>pll;
typedef pair<int,pii>ppii;
typedef pair<ppii,ppii> d_pii;
ppii cal(string s){
    ppii temp;
    string a,b,c;
    a=s[0]; a+=s[1];
    b=s[3];b+=s[4];
    c=s[6];c+=s[7];
    temp.first=stoi(a);
    temp.second=pii(stoi(b),stoi(c));
    return temp;
}
int main(){
    int n;
    while(cin>>n,n){
        vector<pair<ll,ll>>v;
        rep(i,n){
            string s,e; cin>>s>>e;
            ppii start,end;
            start=cal(s);
            end=cal(e);
            ll _start=start.first*3600+start.second.first*60+start.second.second;
            ll _end=end.first*3600+end.second.first*60+end.second.second;
            //cout<<start.first<<":"<<start.second.first<<":"<<start.second.second<<endl;
            //cout<<end.first<<":"<<end.second.first<<":"<<end.second.second<<endl;
            v.push_back(make_pair(_start,_end));
        }
        vl u(v.size());
        rep(i,v.size())u[i]=v[i].first;
        ll ans=0;
        ll base=0;
        rep(i,u.size()){
            ans++;
            base=v[i].second;
            while(true){
                bool update=false;
                vector<ll>::iterator itr=lower_bound(u.begin(), u.end(),base);
                if(itr!=u.end()){
                    int index=(int)(itr-u.begin());
                    update=true;
                    //cout<<*itr<<endl;
                    u.erase(itr);
                    base=v[index].second;
                    v.erase(v.begin()+index);
                }
                if(!update)break;
            }
        }
        cout<<ans<<endl;
    }
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<queue>
using namespace std;
int main(){
  while(1){
    int n;
    string a[10001],b;
    priority_queue<string,vector<string>,greater<string> > c;
    cin>>n;
    if(n==0)break;
    for(int i=0;i<n;i++){
      cin>>a[i]>>b;
      c.push(b);
    }
    sort(a,a+n);
    int cnt=0;
    for(int i=0;i<n;i++){
      if(a[i]>=c.top()){
	c.pop();
      }else cnt++;
    }
    cout<<cnt<<endl;
  }
  return 0;
}

C++: #include <cstdio>
#include <queue>
#include <vector>
#include <map>
using namespace std;

typedef pair<int,int> P;

int main(){
	int n;
	while( scanf("%d", &n) , n ){
		// (時刻,列車の増減) のペアを格納する優先度つきキュー
		// 時刻の早いほうから順に出てくる.
		priority_queue< P , vector<P> , greater<P> > q;
		
		for(int i=0 ; i < n ; i++ ){
			int h1, m1, s1, h2, m2, s2;
			scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
			int t1 = h1 * 60 * 60 + m1 * 60 + s1;
			int t2 = h2 * 60 * 60 + m2 * 60 + s2;
			q.push( P(t1,+1) );
			q.push( P(t2,-1) );
		}
		int ans = 0, cnt = 0;
		while( !q.empty() ){
			cnt += q.top().second;
			q.pop();
			ans = max( ans , cnt );
		}
		printf("%d\n", ans);
	}
}

C++: #include<iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;

int main(){
	int n;
	int m[(24*60*60)+(60*60)+60]={};
	while(cin >> n,n){
		for(int i=0;i<n;i++){
			int bh,bm,bs,eh,em,es;
			scanf("%d:%d:%d %d:%d:%d",&bh,&bm,&bs,&eh,&em,&es);
			m[(bh*60*60)+(bm*60)+bs]+=1;
			m[(eh*60*60)+(em*60)+es]+=-1;
		}
		int count=0,ans=1;
		for(int i=0;i<((24*60*60)+(60*60)+60);i++){
			count+=m[i];
			ans=max(ans,count);
		}
		cout << ans << endl;
	}
}

C++: 
#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<math.h>
#include<string>
#include<string.h>
#include<stack>
#include<queue>
#include<vector>
#include<utility>
#include<set>
#include<map>
#include<stdlib.h>
#include<iomanip>

using namespace std;

#define ll long long
#define ld long double
#define EPS 0.0000000001
#define INF 1e9
#define MOD 1000000007
#define rep(i,n) for(i=0;i<n;i++)
#define loop(i,a,n) for(i=a;i<n;i++)
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)

typedef vector<int> vi;
typedef pair<int,int> pii;

int main(void) {
  int i,j;
  int n;
  while(1){
    cin>>n;
    if(n==0)break;
    pii v[10000];
    string s;
    rep(i,n){
      int a,b;
      cin>>s;
      a=(s[0]-'0')*10+(s[1]-'0');
      a*=60;
      a+=(s[3]-'0')*10+(s[4]-'0');
      a*=60;
      a+=(s[6]-'0')*10+(s[7]-'0');
      cin>>s;
      b=(s[0]-'0')*10+(s[1]-'0');
      b*=60;
      b+=(s[3]-'0')*10+(s[4]-'0');
      b*=60;
      b+=(s[6]-'0')*10+(s[7]-'0');
      v[i].first=a;
      v[i].second=b; 
   }
    sort(v,v+n);
    priority_queue<int> q;
    q.push(-v[0].second);
    loop(i,1,n){
      if(q.top()>=-v[i].first)q.pop();
      q.push(v[i].second);
    }
    cout<<q.size()<<endl;
  }
}