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 rep(i,n) for(int i=0;i<n;i++)
using namespace std;
const int INF=1<<29,MOD=1e9+7;

int main(){
	int day=24*3600+60*60+60;
	int n;
	while(cin>>n&&n){
		int a[day]={};
		for(int i=0;i<2*n;i++){
			int time;
			string s; cin>>s;
			time=(s[0]-'0')*36000+(s[1]-'0')*3600+(s[3]-'0')*600+(s[4]-'0')*60+(s[6]-'0')*10+(s[7]-'0');
			if(i%2==0) a[time]++;
			else a[time]--;
		}
		for(int i=1;i<day;i++){
			a[i]=a[i]+a[i-1];
		}
		sort(a,a+day); reverse(a,a+day);
		cout<<a[0]<<endl;
	}
	return 0;
}

C++: #include <stdio.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <cctype>

#include <iostream>
#include <vector>
#include <deque>
#include <queue>
#include <map>
#include <algorithm>

using namespace std;

#define rep(i, n) for(int i = 0; i < n; i++)
#define repi(i,l,n) for(int (i)=(int)(l);(i)<(int)(n);(i)++)
#define d_arr(arr, h, w) rep(i,(h) ){ cout << "["; rep(j,(w) ) { cout << (arr)[i][j] << ", "; } cout << "]" << endl;}

typedef pair<int ,int> P;

class Train
{
    public:
        int start[3];
        int end[3];

        Train()
        {
            rep(i,3){
                start[i] = 0;
                end[i] = 0;
            }

        }
        Train(int s[3], int e[3])
        {
            rep(i,3){
                start[i] = s[i];
                end[i] = e[i];
            }
        }

        //Coordinates operator+(Coordinates p)
        //{
        //    Coordinates tmp;
        //    tmp.x = x + p.x;
        //    tmp.y = y + p.y;
        //    return tmp;
        //}

        //friend bool operator==(const Coordinates a, const Coordinates b)
        //{
        //    return (a.x == b.x && a.y == b.y);
        //}
        //friend bool operator<(const Coordinates a, const Coordinates b)
        //{
        //    return (a.x < b.x && a.y < b.y);
        //}
        //friend bool operator<=(const Coordinates a, const Coordinates b)
        //{
        //    return (a.x <= b.x && a.y <= b.y);
        //}
};



int main()
{
    int n;
    while( cin >> n, n)
    {
        vector< vector<int> > s_vec;
        vector< vector<int> > e_vec;
        int min_time =24*60*60;
        int max_time =0;
        rep(i,n)
        {
            vector<int> s(3);
            vector<int> e(3);
            scanf("%d:%d:%d",&s[0],&s[1],&s[2]);
            scanf("%d:%d:%d",&e[0],&e[1],&e[2]);
            s_vec.push_back(s);
            e_vec.push_back(e);
            if( s[0]*60*60 + s[1]*60 + s[2] < min_time ) { min_time = s[0]*60*60 + s[1]*60 + s[2]; }
            if( e[0]*60*60 + e[1]*60 + e[2] > max_time)  { max_time = s[0]*60*60 + s[1]*60 + s[2]; }
        }
        vector<int> min(3);
        vector<int> max(3);

        rep(i,3)
        {
            min[i] = s_vec[0][i];
            max[i] = e_vec[n-1][i];
        }
        int max_count = 0;
        //各時間に対して
        for( int i = min_time; i <= max_time; i++)
        {
            int count = 0;
            int now[3];
            now[0] = i/ (60*60);
            now[1] = (i -now[0]) / 60;
            now[2] = (i -now[0]) % 60;
            //confrim
            //各情報に対して
            rep(j,n)
            {
                int s_time = s_vec[j][0]*60*60 + s_vec[j][1]*60 + s_vec[j][2];
                int e_time = e_vec[j][0]*60*60 + e_vec[j][1]*60 + e_vec[j][2];
                if( s_time <= i && i < e_time )
                {
                    count++;
                }
            }
            if (count > max_count) { max_count = count; }
        }
        cout << max_count << endl;
    }
}