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>
#include <algorithm>
#include <cmath>
#include <cstdio>

using namespace std;

int main(){
  while(1){
    int n;
    cin >> n;
    if(n==0)break;
    
    int hs,ms,ss,he,me,se,S[10000],E[10000];
    
    for(int i=0; i < 10000;i++){
      S[i]=0;
      E[i]=0;
    }
    for(int i=0; i < n; i++){
      scanf("%d:%d:%d",&hs,&ms,&ss);
      scanf("%d:%d:%d",&he,&me,&se);  
      S[i]=hs*10000+ms*100+ss;
      E[i]=he*10000+me*100+se;
    }
    int cnt=0,Max=0;
    for(int i=0; i < n-1 ;i++){
      for(int j=i+1; j < n ;j++){
	
	if(E[i] > S[j])cnt++;
	else break;
      }
      Max = max(Max,cnt);
      cnt = 0;
    }
    cout << Max+1 << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <map>
using namespace std;

typedef pair< int, int > iP;

int main() {

    int n;

    while(cin >> n, n) {
        vector< iP > v;
        for(int i = 0; i < n; i++) {
            int h, m, s, hh, mm, ss;
            scanf("%2d:%2d:%2d %2d:%2d:%2d", &h, &m, &s, &hh, &mm, &ss);
            v.push_back(iP(h * 3600 + m * 60 + s, hh * 3600 + mm * 60 + ss));
        }

        int cnt = 1;
        vector< bool > dep(n, false);
        vector< bool > used(n, false);
        dep[0] = used[0] = true;
        for(int i = 0; i < n; i++) {
            if(dep[i]) {
                for(int j = i + 1; j < n; j++) {
                    if(!used[j] && v[i].second > v[j].first) {
                        cnt++;
                        used[j] = true;
                        dep[j] = true;
                    }
                }
            }
        }
        cout << cnt << endl;
    }
}

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

int time[60*60*24];
	
int main(void){
	int n;
	while(cin >> n,n){
		for(int i=0;i<60*60*24;i++)
			time[i]=0;
		for(int j=0;j<n;j++){
			string l,a;
			cin >> l >> a;
			int lh=atoi(l.substr(0,2).c_str());
			int lm=atoi(l.substr(3,2).c_str());
			int ls=atoi(l.substr(6,2).c_str());
			int ah=atoi(a.substr(0,2).c_str());
			int am=atoi(a.substr(3,2).c_str());
			int as=atoi(a.substr(6,2).c_str());
			int from=lh*60*60+lm*60+ls;
			int to=ah*60*60+am*60+as;
			for(int i=from;i<to;i++)
				time[i]++;
		}
		int cmax=0;
		for(int i=0;i<60*60*24;i++)
			cmax=max(cmax,time[i]);
		cout << cmax << endl;
	}
	return 0;
}

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

int main(){
	
	while(1){
		int n;
		cin>>n;
		if(n==0)break;
		//getchar();
		cin.ignore();
		
		string s;
		vector<int> imo(86401,0);
		for(int i=0;i<n;i++){
			getline(cin,s);
			int st=((s[0]-'0')*10+(s[1]-'0'))*60*60+((s[3]-'0')*10+(s[4]-'0'))*60+((s[6]-'0')*10+(s[7]-'0'));
			int gt=((s[9]-'0')*10+(s[10]-'0'))*60*60+((s[12]-'0')*10+(s[13]-'0'))*60+((s[15]-'0')*10+(s[16]-'0'));
			//cout<<st<<" "<<gt<<endl;
			imo[st]++;
			imo[gt]--;
		}
		
		int tmp=0;
		int ans=0;
		
		for(int i=0;i<86401;i++){
			tmp+=imo[i];
			ans=max(ans,tmp);
		}
		
		cout<<ans<<endl;
	}
	
	
	return 0;
}

C++: #include <algorithm>
#include <cstdio>
#include <vector>
using namespace std;

int main() {
    const int MAX = 60 * 60 * 24;
    int n;
    while (scanf("%d", &n), n) {
        vector<int> imos(MAX + 1);
        while (n--) {
            int h1, m1, s1, h2, m2, s2;
            scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
            int s = h1 * 3600 + m1 * 60 + s1;
            int t = h2 * 3600 + m2 * 60 + s2;
            imos[s]++, imos[t]--;
        }
        for (int i = 1; i <= MAX; i++) imos[i] += imos[i - 1];
        int ma = 0;
        for (int i = 0; i < MAX; i++) ma = max(ma, imos[i]);
        printf("%d\n", ma);
    }
    return 0;
}

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

typedef long long ll;

ll f(string s){
    string s1,s2,s3;
    s1 = s.substr(0,2);
    s2 = s.substr(3,2);
    s3 = s.substr(6,2);

    int hh = stoi(s1)*3600;
    int mm = stoi(s2)*60;
    int ss = stoi(s3)*1;

    return hh+mm+ss;
}

const int mx=23*3600+59*60+59;

void solve(int n){
    vector<int> v(mx+10,0);
    for(ll i=0;i<n;i++){
        string s1,s2;
        cin >> s1 >> s2;
        ll s=f(s1);
        ll t=f(s2);
        v[s]++;
        v[t]--;
    }
    for(int i=1;i<mx+10;i++){
        v[i] = v[i] + v[i-1];
    }
    int ans = 0;
    for(int i=0;i<mx+10;i++){
        ans = max(ans,v[i]);
        if(v[i] == 6)  cout << i << endl;
    }
    cout << ans << endl;
}

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