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 n,a[240001],ans;
string s,t;
int f(string s){
    int S=(s[0]-'0')*100000+(s[1]-'0')*10000+(s[3]-'0')*1000+(s[4]-'0')*100+(s[6]-'0')*10+(s[7]-'0');
    return S;
}
int main(void){
    while(1){
    cin>>n;
    if(n==0)return 0;
    for(int i=0;i<=240000;i++)a[i]=0;
    for(int i=0;i<n;i++){
        cin>>s>>t;
        //cout<<f(s)<<endl;
        a[f(s)]+=1;
        a[f(t)]+=-1;
    }
    ans=a[0];
    for(int i=0;i<240000;i++){
        a[i+1]+=a[i];
        ans=max(ans,a[i+1]);
    }
    cout<<ans<<endl;
    }
}

C++: #include<bits/stdc++.h>
using namespace std;

int main(){
  
  while(1){
    int n=0;
    cin >> n;
    if(n==0)break;
    int time[1000000] = {};
    for(int i=0;i<1000000;i++){
      time[i] =0;

    }
    
    for(int i=0;i<n;i++){
      
      int h,m,s;
      char c;
      c =0;
      cin >> h >> c >> m >> c >> s;

      int a = h * 3600 + m * 60 + s;

      time[a]++;

      cin >> h >> c >> m >> c >> s;

      a = h * 3600 + m * 60 + s;

      time[a]--;
    }

    int cnt,mx;
    mx =0;
    cnt= 0;
    for(int i=0;i<1000000;i++){
      cnt += time[i];
      mx = max(mx,cnt);
    }
    cout << mx << endl;

  }




}