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++: // AOJ 2013

#include <iostream>

using namespace std;

int data[24][60][60];

int main(void)
{
	int n;
	while (cin >> n, n){
		for (int i = 0; i < 24; i++){
			for (int j = 0; j < 60; j++){
				for (int k = 0; k < 60; k++){
					data[i][j][k] = 0;
				}
			}
		}

		int s[3], e[3];
		for (int i = 0; i < n; i++){
			scanf("%d:%d:%d %d:%d:%d", &s[0], &s[1], &s[2], &e[0], &e[1], &e[2]);
			int h = s[0], m = s[1], sec = s[2];
			data[h][m][sec] += 1;
			while (1){
				if (h == e[0] && m == e[1] && sec == e[2]){
					data[h][m][sec]--;
					break;
				}
				sec++;
				if (sec == 60){
					m++;
					sec = 0;
				}
				if (m == 60){
					h++;
					m = 0;
				}
				data[h][m][sec] += 1;
			}
		}
/*
		for (int i = 0; i < 24; i++){
			for (int j = 0; j < 60; j++){
				int cnt = 0;
				for (int k = 0; k < 60; k++){
					cnt = max(cnt, data[i][j][k]);
				}
				cout << cnt << " ";
			}
			puts("");
		}
*/
		int ret = 0;
		for (int i = 0; i < 24; i++){
			for (int j = 0; j < 60; j++){
				for (int k = 0; k < 60; k++){
					ret = max(ret, data[i][j][k]);
				}
			}
		}
		cout << ret << endl;
	}

	return 0;
}

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

int main(){
  int time[100000];

  int n;
  while(cin>>n,n!=0){
      memset(time,0,sizeof(time));
      for(int i = 0;i<n;i++){
	int h,m,s;
	scanf("%d:%d:%d",&h,&m,&s);
	time[h * (60*60) + m * 60 + s]++;
	scanf("%d:%d:%d",&h,&m,&s);
	time[h * (60*60) + m * 60 + s]--;
      }
      for(int i = 1;i<=24*60*60;i++){
	time[i] += time[i-1];
      }
      cout<<*max_element(time,time+24*60*60)<<endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>

#ifdef DEBUG
#define debug(x) cout << #x << ": " << x << endl
#else
#define debug(x)
#endif

#define REP(i, n) for(int i = 0; i < (n); i++)
#define REPS(i, n) for(int i = 1; i <= (n); i++)
#define ALL(v) (v).begin(), (v).end()

#define pb push_back
#define mp make_pair
#define mt make_tuple

using namespace std;

using ll = long long;
using pi = pair<int, int>;
using pl = pair<ll, ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vs = vector<string>;

const ll INF = 1e18;
const ll MOD = 1e9+7;

template<class T> inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return true;} return false; }
template<class T> inline bool chmin(T &a, const T &b) { if (a>b) { a = b; return true;} return false; }


signed main()
{
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    while(true)
    {
        int n; cin >> n;
        if(n == 0) break;
        vi imos(250000);
        REP(i, n)
        {
            string s, t; cin >> s >> t;
            s.erase(5, 1); s.erase(2, 1);
            t.erase(5, 1); t.erase(2, 1);
            int x = stoi(s), y = stoi(t);
            imos[x]++; imos[y]--;
        }
        REP(i, imos.size()-1) imos[i+1] += imos[i];
        cout << *max_element(ALL(imos)) << endl;
    }
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<tuple>

using namespace std;
typedef pair<int, int> pii;

int main(){

    while(1){
        int n;
        cin>> n;
        if(!n) break;

        string s[n], t[n];
        for(int i=0; i<n; i++) cin>> s[i]>> t[i];
        int a[n], b[n];
        for(int i=0; i<n; i++){
            a[i]=60*60*stoi(s[i].substr(0, 2))+60*stoi(s[i].substr(3, 2))+stoi(s[i].substr(6, 2));
            b[i]=60*60*stoi(t[i].substr(0, 2))+60*stoi(t[i].substr(3, 2))+stoi(t[i].substr(6, 2));
        }
        int v[24*60*60]={};
        for(int i=0; i<n; i++){
            v[a[i]]+=1;
            v[b[i]]-=1;
        }
        for(int i=1; i<24*60*60; i++){
            v[i]+=v[i-1];
        }
        int k=0;
        for(int i=0; i<24*60*60; i++){
           	k=max(k, v[i]);
        }
        cout<< k<< endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define each(a, b) for(auto (a): (b))
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
#define pb push_back
#define show(x) cout <<#x<<" = "<<(x)<<endl
#define spair(p) cout <<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(i,v.size())cout<<" "<<v[i];cout<<endl
#define sset(s) cout<<#s<<":";each(i,s)cout <<" "<<i;cout<<endl

using namespace std;

typedef pair<int,int>P;

const int MAX_N = 100005;

int n;
int a[24*60*60+1];

int tt(string s1)
{
    string ss;
    ss = s1.substr(0,2);
    int h = stoi(ss);
    ss = s1.substr(3,2);
    int m = stoi(ss);
    ss = s1.substr(6,2);
    int s = stoi(ss);
    return h*60*60 + m*60 + s;
}

int main()
{
    while(1){
        cin >> n;
        if(n == 0){
            break;
        }
        rep(i,24*60*60+1){
            a[i] = 0;
        }
        rep(i,n){
            string s1,s2;
            cin >> s1 >> s2;
            a[tt(s1)]++,a[tt(s2)]--;
        }
        int res = 0;
        int nw = 0;
        rep(i,24*60*60+1){
            nw += a[i];
            res = max(res,nw);
        }
        cout << res << "\n";
    }
}