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 <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define INF 1000000000
#define rep(i,a,b) for (int i=(a);i<(b);i++)
#define rev(i,a,b) for (int i=(a)-1;i>=b;i--)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef queue<int> qi;
typedef vector<int> vi;
typedef vector<string> vs;
int dx[4] = { 0, 1, 0, -1 };
int dy[4] = { 1, 0, -1, 0 };

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

		vector<pii> vp;
		rep(i,0,n) {
			int h,m,s;
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, 1));
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, -1));
		}

		sort(vp.begin(), vp.end());

		int ans = 0, tmp = 0;
		rep(i,0,vp.size()) {
			tmp += vp[i].second;
			ans = max(ans, tmp);
		}
		cout << ans << endl;
	}
}

C++: #include <iostream>
#define REP(i,s,n) for(int i=s;i<n;++i)
#define rep(i,n) REP(i,0,n)
#define MAX 10000
using namespace std;
int ans,cou;
int n;
char s[10],g[10];
struct t {
  int h;
  int m;
  int s;
};
t start[MAX],goal[MAX];
int main() {
  while(true){
    cin >> n;
    if(n==0) return 0;
    ans = 0;
    cou = 0;
    rep(i,n){
      cin >> s >> g;
      start[i] = t();
      goal[i] = t();
      start[i].h = (int)(s[0]-'0')*10+(int)(s[1]-'0');
      start[i].m = (int)(s[3]-'0')*10+(int)(s[4]-'0');
      start[i].s = (int)(s[6]-'0')*10+(int)(s[7]-'0');
      goal[i].h = (int)(g[0]-'0')*10+(int)(g[1]-'0');
      goal[i].m = (int)(g[3]-'0')*10+(int)(g[4]-'0');
      goal[i].s = (int)(g[6]-'0')*10+(int)(g[7]-'0');
    }
    rep(i,24) rep(j,60) rep(k,60){
      rep(l,n){
        if(goal[l].h==i&&goal[l].m==j&&goal[l].s==k) cou--;
        if(start[l].h==i&&start[l].m==j&&start[l].s==k) cou++;
      }
      if(cou>ans) ans = cou;
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <utility>
#include <vector>
#include <algorithm>

using namespace std;

int hhmmss_to_i(int h, int m, int s) {
  return (h * 60 + m) * 60 + s;
}

int main() {
  int n;
  while (scanf("%d", &n) != EOF && n) {
    vector<pair<int,bool>> V; // firstは時刻、boolは出発ならtrue、到着ならfalse
    for (int i=0; i<n; i++) {
      int h, m, s;
      scanf("%02d:%02d:%02d", &h, &m, &s);
      int t = hhmmss_to_i(h, m, s);
      V.push_back(make_pair(t, true));
      scanf("%02d:%02d:%02d", &h, &m, &s);
      t = hhmmss_to_i(h, m, s);
      V.push_back(make_pair(t, false));
    }
    sort(V.begin(), V.end());
    int count = 0;
    int max = 0;
    for (unsigned int i=0; i<V.size(); i++) {
      if (V[i].second) {
	count++;
	if (max < count) max = count;
      } else {
	count--;
      }
    }
    printf("%d\n", max);
  }
}

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

//define
#define ALL(a) a.begin(),a.end()
#define REP(i,n) for(int i=0;i<n;i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)
#define debug(x) if(1) cout<<#x<<":"<<x<<endl;
#define DEBUG(x) if(1) cout<<#x<<":"<<x<<endl;
#define ll long long

//constant
const int MOD=1000000007;
const int INF=INT_MAX/3-1;
const double EPS=1e-9;
const int dx[]={1,0,-1,0};
const int dy[]={0,1,0,-1};

//typedef
typedef vector<int> vi;
typedef vector<vector<int>> vvi;






int main(){
    int n;
    while(cin>>n,n){
        vector<pair<int,bool>> timer;
        string buf;
        REP(i,n){
            REP(j,2){
            cin>>buf;
            int hh=stoi(buf.substr(0,2));
            int mm=stoi(buf.substr(3,2));
            int ss=stoi(buf.substr(6,2));
            timer.push_back(make_pair(ss+mm*60+hh*60*60,j));
            }

        }
        sort(ALL(timer),[](pair<int,bool> lef,pair<int,bool> rig)
        {return lef.first<rig.first ||
                lef.first==rig.first && lef.second;});
        int running=0;
        int stop=0;
        REP(i,n*2){
            if(!timer[i].second){
                if(stop)
                    stop--;
                else
                    running++;


            }
 else if(timer[i].second){
                stop++;


            }



        }
            cout<<running<<endl;




    }




    return 0;
}

C++: #include <cstdio>
#include <vector>
#include <map>
#include <algorithm>

template <class T1, class T2>
struct pair_first_less {
	bool operator()(const std::pair<T1, T2> &x, const std::pair<T1, T2> &y) const {
		return x.first < y.first;
	}
};

void input(std::vector< std::pair<int, int> > *t, int n)
{
	for (int i = 0; i < n; ++i) {
		int h0, m0, s0, h1, m1, s1;
		scanf("%02d:%02d:%02d %02d:%02d:%02d", &h0, &m0, &s0, &h1, &m1, &s1);
		const int t0 = (h0 * 60 + m0) * 60 + s0;
		const int t1 = (h1 * 60 + m1) * 60 + s1;
		t->push_back(std::pair<int, int>(t0, t1));
	}
}

int answer(const std::vector< std::pair<int, int> > &t)
{
	std::vector< std::pair<int, int> > f;	// 
	for (std::vector< std::pair<int, int> >::const_iterator it = t.begin(); it != t.end(); ++it) {
		f.push_back(std::pair<int, int>(it->first, 1));
		f.push_back(std::pair<int, int>(it->second, -1));
	}
	std::sort(f.begin(), f.end(), pair_first_less<int, int>());
	int n_max = 0, n = 0;
	for (std::vector< std::pair<int, int> >::iterator it = f.begin(); it != f.end(); ++it) {
		n += it->second;
		if (n > n_max) { n_max = n; }
	}
	return n_max;
}

int main()
{
	int n;
	while (scanf("%d", &n), n > 0) {
		std::vector< std::pair<int, int> > t;
		input(&t, n);
		printf("%d\n", answer(t));
	}
	return 0;
}