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<bits/stdc++.h>
#define INF 2000000000
#define int long long int
#define MOD 1000000007
#define pb push_back
#define cin1(n) (cin >> n)
#define cin2(a,b) (cin >> a >> b)
#define cin3(a,b,c) (cin >> a >> b >> c)
#define cout(n) (cout << n << endl)
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define fr first 
#define sc second 
#define EPS (1e-10)

using namespace std;

typedef vector<int> vi;
typedef vector< vector<int> > vvi;
typedef vector<pair<int,int>> vpii;
typedef vector<string> vs;
typedef vector<vector<string>> vss;
typedef pair<int,int> pii;

int dx[] = {1,-1,0,0};
int dy[] = {0,0,1,-1};
int n,m;
int a,b;
int p,q;

pii input(string t1,string t2) {
	int ret1,ret2;

	ret1 = stoi(t1.substr(6,2)) + 60 * stoi(t1.substr(3,2)) + 60 * 60 * stoi(t1.substr(0,2));
	ret2 = stoi(t2.substr(6,2)) + 60 * stoi(t2.substr(3,2)) + 60 * 60 * stoi(t2.substr(0,2));
	return make_pair(ret1,ret2);
}

signed main() {

	while(1) {
		cin1(n);
		if (n == 0) break;

		vpii table(n,make_pair(0,0));
		rep(i,0,n) {
			string time1,time2;
			cin2(time1,time2);
			table[i] = input(time1,time2);	
			//cout << table[i].fr << " " << table[i].sc << endl;
		}
		
		int idx = 0;
		vector<pair<bool,int>> train;
		train.pb(make_pair(true,0));
		rep(i,0,60*60*24) {
			//std::cout << "table.fr " << table[idx].fr <<  std::endl;
			rep(j,0,train.size()) {
				if (train[j].sc == i) {
					train[j].fr = true;
				}
			}
			if (table[idx].fr == i) {
				//cout << "idx = " << idx << endl;
				//cout << "i = " << i << endl;
				//cout(table[idx].fr);
				bool flag = false;
				rep(j,0,train.size()) {
					if (train[j].fr) {
						train[j].fr = false;
						train[j].sc = table[idx].sc;
						flag = true;
						break;
					}
				}
				if (!flag) {
					train.pb(make_pair(false,table[idx].sc));
				}
				idx++;
				i--;
			}
		}
		cout(train.size());
	}

	return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
static const int N = 10000;
int Change(string);
int main(){
  int n,cnt,check[N],ok,flag,Max,sh[N],sm[N],ss[N],eh[N],em[N],es[N],i,j;
  int comh,comm,coms;
  string start[N],end[N],sub;
  while(1){
    cin >> n;
    cnt=0;
    if(n==0) break;
    for(i=0;i<n;i++){
      cin >> start[i] >> end[i];
      check[i]=-1;
      sub=start[i].substr(0,2);
      sh[i]=Change(sub);
      sub=start[i].substr(3,2);
      sm[i]=Change(sub);
      sub=start[i].substr(6,2);
      ss[i]=Change(sub);
      sub=end[i].substr(0,2);
      eh[i]=Change(sub);
      sub=end[i].substr(3,2);
      em[i]=Change(sub);
      sub=end[i].substr(6,2);
      es[i]=Change(sub);
    }
    for(i=0;i<n;i++){
      if(check[i]==-1){
	check[i]=i;
	comh=eh[i];
	comm=em[i];
	coms=es[i];
	for(j=i+1;j<n;j++){
	  if(check[j]==-1){
	    ok=0;
	    if(comh==sh[j]){
	      if(comm==sm[j]){
		if(coms<=ss[j]) ok=1;
	      }
	      else if(comm<sm[j]) ok=1;
	    }
	    else if(comh<sh[j]) ok=1;
	    if(ok==1){
	      check[j]=i;
	      comh=eh[j];
	      comm=em[j];
	      coms=es[j];
	    }
	  }
	}
      }
    }
    Max=0;
    for(i=0;i<n;i++){
      Max=max(Max,check[i]);
    }
    cout << Max+1 << endl;
  }
  return 0;
}
int Change(string sub){
  int ret=0,x=1,i;
  for(i=0;i<2;i++){
    ret=ret*x+(sub[i]-'0');
    x=10;
  }
  return ret;
}

C++: #include <iostream>
#define REP(i, a, n) for(int i = (a); i < (n); i++)
using namespace std;

int N;

int input() {
  string S;
  cin >> S;
  int h, m, s;
  h = (S[0] - '0') * 10 + (S[1] - '0');
  m = (S[3] - '0') * 10 + (S[4] - '0');
  s = (S[6] - '0') * 10 + (S[7] - '0');
  return h * 3600 + m * 60 + s;
}

int main(void) {
  while(cin >> N, N) {
    int T[10000], U[10000];
    REP(i, 0, N) {
      T[i] = input();
      U[i] = input();
    }

    int ans = 0;
    for(int i = 0, j = 0; i < N; i++) {
      while(j < N && T[j] < U[i]) {
        j++;
      }
      ans = max(ans, j - i);
    }
    cout << ans << endl;
  }
  return 0;
}

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

int main(){
    int n;
    while(true){
        cin >> n;
        if(n == 0){
            break;
        }
        
        vector<int> train;
        train.push_back(0);
        
        int hs, ms, ss, he, me, se;
        int time1, time2;
        int ans = 1;
        char tmp;
        for(int i=0; i<n; i++){
            cin >> hs >> tmp >> ms >> tmp >> ss;
            cin >> he >> tmp >> me >> tmp >> se;
            time1 = hs*3600 + ms*60 + ss;
            time2 = he*3600 + me*60 + se;
            int sz = train.size();
            for(int j=0; j<sz; j++){
                if(train[j] <= time1){
                    train[j] = time2;
                    break;
                }
                if(j == train.size()-1){
                    train.push_back(time2);
                    ans++;
                }
            }
        }
        cout << ans << endl;
    }
    
  return 0;
}

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

int main() {
  int n;
  int res = 0;
  int h1, m1, s1;
  int h2, m2, s2;

  while(cin >> n, n!=0){
    signed int time[24*3600+60*60+60] = {0};
    for(int i = 0; i < n; i++) {
      scanf("%d:%d:%d", &h1, &m1, &s1);
      scanf("%d:%d:%d", &h2, &m2, &s2);
      time[h1*3600+m1*60+s1]++;
      time[h2*3600+m2*60+s2]--;
    }

    for(int i = 0; i < 24*3600+60*60+60; i++) {
      time[i+1]+=time[i];
      if(res < time[i+1])
        res = time[i+1];
    }
    cout << res << endl;
  }
  return 0;
}