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 <iostream>
using namespace std;

int main() {
  while(1) {
    int n;
    cin >> n;
    if(n == 0) break;

    int limit = 24*3600;
    int data[limit];
    for(int i = 0; i < limit; i++) {
      data[i] = 0;
    }

    for(int i = 0; i < n; i++) {
      int h, m, s;
      int ss, gs;
      scanf("%d:%d:%d", &h, &m, &s);
      ss = h*3600 + m*60 +s;
      scanf("%d:%d:%d", &h, &m, &s);
      gs = h*3600 + m*60 +s;
      for(int j = ss; j < gs; j++) {
	data[j]++;
      }
    }

    int max = -1;
    for(int i = 0; i < limit; i++) {
      if(data[i] > max) max = data[i];
    }

    cout << max << endl;
  }
  return 0;
}

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

int main(){
	while(true){
		int m,pool=0,total=0;
		multiset<string> run;
		cin>>m;
		if(m==0)break;
		for(int i=0;i<m;i++){
			string dep,arv;
			cin>>dep>>arv;
			run.insert(arv);
			for(multiset<string>::iterator ita=run.begin();(*ita)<=dep;){
				pool++;
				ita=run.erase(ita);
			}
			if(pool==0){
				total++;
			}else{
				pool--;
			}
		}
		cout<<total<<endl;
	}
	return 0;
}

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

using namespace std;

struct Event {
  int time, type;
  Event(int type, int time): type(type), time(time){;}
  bool operator<(const Event &rhs) const {
    if (time == rhs.time)
      return type < rhs.type;
    else
      return time < rhs.time;
  }
};

int main()
{
  int N;
  while (cin >> N && N) {
    vector<Event> vec;
    for (int i = 0; i < N; i++) {
      int h, m, s, b, e;
      scanf("%d:%d:%d", &h, &m, &s);
      vec.push_back(Event(0, h * 60 * 60 + m * 60 + s));
      scanf("%d:%d:%d", &h, &m, &s);
      vec.push_back(Event(1, h * 60 * 60 + m * 60 + s - 1));
    }

    sort(vec.begin(), vec.end());
    int ans = 0, cnt = 0;
    for (int i = 0; i < vec.size(); i++) {
      Event e = vec[i];
      if (e.type == 0)
        cnt++;
      else
        cnt--;
      ans = max(ans, cnt);
    }

    cout << ans << endl;
  }
}

C++: #include <functional>
#include <algorithm>
#include <iostream>
#include <numeric>
#include <iomanip>
#include <utility>
#include <cstdlib>
#include <sstream>
#include <bitset>
#include <vector>
#include <cstdio>
#include <ctime>
#include <queue>
#include <deque>
#include <cmath>
#include <stack>
#include <list>
#include <map>
#include <set>

using namespace std;

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

#define dump(x)  cerr << #x << " = " << (x) << endl
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back



int main(){
    int n;
    while(cin>>n){
        int data[100000]={};
        if(n==0)break;
        
        rep(i,n){
            char ch;
            int a,aa,aaa,b,bb,bbb;
            cin>>a>>ch>>aa>>ch>>aaa>>b>>ch>>bb>>ch>>bbb;
            data[a*60*60+aa*60+aaa]+=1;
            data[b*60*60+bb*60+bbb]-=1;
        }
        for(int i=1;i<40000;i++){
            data[i]=data[i]+data[i-1];
        }
        
        int ans=-1;
        rep(i,40000){
            ans=max(ans,data[i]);
        }
        cout<<ans<<endl;
    }
    
    return 0;
}