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
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>
#include <queue>

using namespace std;

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);

int main(){
  int N;
  while(cin >> N, N){
	//vector<PII> tms;
	int range[24*60*60+1];
	fill(range, range+24*60*60+1, 0);
	REP(i,N){
	  int h[2], m[2], s[2];
	  scanf("%2d:%2d:%2d", &h[0], &m[0], &s[0]);
	  scanf("%2d:%2d:%2d", &h[1], &m[1], &s[1]);
	  int st = h[0]*60*60+m[0]*60+s[0], et = h[1]*60*60+m[1]*60+s[1];
	  ++range[st], --range[et];
	}
	//SORT(tms);
	int ans = 0, acc = 0;
	REP(i,24*60*60){
	  acc += range[i];
	  ans = max(ans, acc);
	}
	cout << ans << endl;
  }  
  
  return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 10e9+9
#define EPS 1e-10
#define MAX_N 100100
#define MAX_M 100100

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;
typedef pair<P, char> PC;

int n, h, m, s;
int a[100000];

int main(){
	while (cin >> n&&n){
		fill(a, a + 100000, 0);
		REP(i, n){
			scanf("%d:%d:%d", &h, &m, &s);
			a[h * 3600 + m * 60 + s]++;
			scanf("%d:%d:%d", &h, &m, &s);
			a[h * 3600 + m * 60 + s]--;
		}
		FOR(i, 1, 100000){
			a[i] += a[i - 1];
		}
		int ans = 1;
		REP(i, 100000){
			ans = max(ans, a[i]);
		}
		cout << ans << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
int main(){
	int n,i,b[6];
	while(cin>>n,n){
		int a[86400]={0},ans=0,s=0;
		while(n--){
			scanf("%d:%d:%d %d:%d:%d",&b[0],&b[1],&b[2],&b[3],&b[4],&b[5]);
			a[b[0]*3600+b[1]*60+b[2]]++;
			a[b[3]*3600+b[4]*60+b[5]]--;
		}
		for(i=0;i<86400;i++){
			s+=a[i];
			ans=max(ans,s);
		}
		cout<<ans<<endl;
	}
}

C++: #include<iostream>
#define mp make_pair
#include<cstdio>
#define MAX 86400
#include<map>
#include<algorithm>
#include<cstdlib>
#include<string>
using namespace std;
typedef pair<int,int> P;
int main(){
	int n,l,a;
	char s[20];
	P table[20000];
	while(cin>>n,n){
		for(int i=0;i<n;i++){
			cin>>s;
			l=atoi(s)*3600+atoi(&s[3])*60+atoi(&s[6]);
			table[i]=P(l,1);
			cin>>s;
			a=atoi(s)*3600+atoi(&s[3])*60+atoi(&s[6]);
			table[i+n]=P(a,0);
		}
		int now=0,ans=0;
		sort(table,table+2*n);
		for(int i=0;i<2*n;i++){
			if(table[i].second)
			now++;
			else now--;
			ans=max(now,ans);
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;
typedef pair<int,int> se;
typedef vector<se> tt;
int main(){
  int n;
  cin>> n;
  while(n!=0){
    int i,j,k;
    int map[86401]={};
    string str;
    tt t;
    for(i=0;i<n;i++){
      int st=0,et=0;
      cin >> str;
      st+=((str[0]-'0')*10+str[1]-'0')*24*60;
      st+=((str[3]-'0')*10+str[4]-'0')*60;
      st+=((str[6]-'0')*10+str[7]-'0');
      cin >> str;
      et+=((str[0]-'0')*10+str[1]-'0')*24*60;
      et+=((str[3]-'0')*10+str[4]-'0')*60;
      et+=((str[6]-'0')*10+str[7]-'0');
      t.push_back(make_pair(st,et));
    }
    //sort(t.begin(),t.end());
    int m=0,b;
    for(j=0;j<86401;j++) {
      b=0;
      for(k=0;k<t.size();k++){
	if(t[k].first<=j&&j<t[k].second) b++;
      }
      if(m<b) m=b;
    }
    cout << m << endl;
    cin >> n;
  }
  return 0;
}