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<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<cassert>
#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<queue>
#include<set>
#include<map>
#include<utility>
#include<numeric>
#include<algorithm>
#include<bitset>
#include<complex>
#include<stack>

using namespace std;

typedef long long Int;
typedef vector<int> vint;
typedef pair<int,int> pint;
typedef vector<string> vstring;
typedef vector<pint> vpint;

struct Edge{int to,from,cost;};

#ifdef DEBUG
#define debug cout
#else
stringstream __ss__;
#define debug __ss__
#endif

template<class T> void pv(T a, T b) { for (T i = a; i != b; ++i) debug << *i << " "; debug << endl; }
template<class T> void chmin(T &t, T f) { if (t > f) t = f; }
template<class T> void chmax(T &t, T f) { if (t < f) t = f; }
int in() { int x; scanf("%d", &x); return x; }

#define rep(i,n) for(int i=0;i<(n);++i)
#define repd(i,n) for(int i=(n)-1;i>=0;i--)
#define repn(i,m,n) for(int i=(m);i<=(n);++i)
#define repnd(i,m,n) for(int i=(n)-1;i>=(m);i--)
#define rep0(i,n) for(i=0;i<(n);++i)
#define all(n) n.begin(),n.end()
#define sz(n) ((int)(n).size())
#define IL for(;;)
#define MP make_pair
#define PB push_back
#define SS stringstream
#define X second
#define Y first
#define PUTLINE debug<<"LINE:"<<__LINE__<<endl;

const int INF = 2147483647/3;
const double EPS = 1e-10;
const double PI = acos(-1.0);

const int dx[]={1,-1,0,0,1,-1,1,-1,0};
const int dy[]={0,0,1,-1,1,-1,-1,1,0};

vint train;

int main() {
	IL{
		train.clear();
		int n=in();
		if(n==0)break;
		string f,t;
		int from,to;
		rep(i,n){
			cin>>f>>t;
			from=(f[0]-'0')*100000+(f[1]-'0')*10000+(f[3]-'0')*1000+(f[4]-'0')*100+(f[6]-'0')*10+f[7]-'0';
			to=(t[0]-'0')*100000+(t[1]-'0')*10000+(t[3]-'0')*1000+(t[4]-'0')*100+(t[6]-'0')*10+t[7]-'0';
			if(sz(train)>0&&train[0]<=from){
				train[0]=to;
			}else{
				train.PB(to);
			}
			sort(all(train));
		}
		cout<<sz(train)<<endl;
	}
	return 0;
}

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

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

typedef pair<int,int> pii;

vector<pii>train;
const int H=60*60;
const int M=60;
const int S=1;
int unit[3]={H,M,S};

int getTime(string s){
  string tmp;
  int res=0;
  for(int i=0;i<3;i++){
    tmp=s.substr(3*i,2);
    int val=unit[i]*atoi(tmp.c_str());
    res+=val;
  }
  return res;
}

void makeEvent(string start,string arrival){
  int st=getTime(start);
  int at=getTime(arrival);
  train.push_back(make_pair(st,1));
  train.push_back(make_pair(at,0));
}

int main(){
  int n;
  while(cin>>n,n){
    for(int i=0;i<n;i++){
    string start,arrival;
    cin>>start>>arrival;
    makeEvent(start,arrival);
    }
    int ans=0,tmp=0;
    sort(train.begin(), train.end());
    for(pii i:train){
      if(i.second==1){
	tmp++;
      }else{
	tmp--;
      }
      ans=max(tmp,ans);
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#define N 10000
using namespace std;
int Change(string);
int Num(string);
struct data{
  int a,b;
  bool operator<(const data & right)const{
    if(b>right.b) return b<right.b;
    return a<right.a;
  }
};
int main(){
  int n,ch[N],cnt,com,i,j;
  string stra,strb;
  struct data d[N];
  while(1){
    cin >> n;
    if(n==0) break;
    for(i=0;i<n;i++){
      cin >> stra >> strb;
      d[i].a=Change(stra);
      d[i].b=Change(strb);
      ch[i]=0;
    }
    sort(d,d+n);
    cnt=0;
    for(i=0;i<n;i++){
      if(ch[i]==0){
	ch[i]=1;
	com=d[i].b;
	cnt++;
	for(j=i+1;j<n;j++){
	  if(com<=d[j].a){
	    if(ch[j]==0){
	      ch[j]=1;
	      com=d[j].b;
	    }
	  }
	}
      }
    }
    cout << cnt << endl;
  }
  return 0;
}
int Change(string str){
  int d;
  string a,b,c;
  a=str.substr(0,2);
  b=str.substr(3,2);
  c=str.substr(6,2);
  d=Num(a+b+c);
  return d;
}
int Num(string str){
  int len=str.size(),x=10,i=0,ret=0;
  while(len){
    ret=ret*x+(str[i]-'0');
    i++;
    len--;
  }
  return ret;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>

using namespace std;

struct P {
	int s, e;
	P() {};
	P(int s, int e) : s(s), e(e) {}
};
bool operator <(const P& p1, const P& p2) {
	return p1.e < p2.e;
}

int GetTime() {
	int h, m, s;
	scanf("%d:%d:%d", &h, &m, &s);
	return (h * 60 + m) * 60 + s;
}
int main() {
	int n;
	while ( cin >> n, n ) {
		vector<P> v;
		for (int i = 0; i < n; ++i) {
			int s = GetTime();
			int e = GetTime();
			v.push_back( P(s, e) );
		}
		sort( v.begin(), v.end() );

		vector<int> ans;
		for (int i = 0; i < n; ++i) {
			int pos = -1;
			int E = -1;
			for (int j = 0; j < ans.size(); ++j) {
				if (ans[j] <= v[i].s && ans[j] > E) {
					pos = j;
					E = ans[j];
				}
			}
			if (pos < 0) {
				ans.push_back(v[i].e);
			}
			else {
				ans[pos] = v[i].e;
			}
/*			vector<int>::iterator it = upper_bound(ans.begin(), ans.end(), v[i].s);
			if (it == ans.begin() || --it == ans.begin() ) {
				ans.push_back(v[i].e);
			}
			else {
				*it = v[i].e;
			}
*/
		}
		cout << ans.size() << endl;
	}
}