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 <cstdio>
#include <iostream>
#include <cmath>
#include <ctype.h>
#include <string> 
#include <sstream>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <map>
#include <queue>
#include <utility>
#include <vector>
#include <set>
 
using namespace std;

int HourtoMin(string s);

int main()
{
    int n;
    while(1){
        cin >> n;
        if(n == 0) break;
        int time_s;
        string h_m_s;
        vector<pair<int, int> > trains(20001);
        for(int i = 0; i < 2 * n; i++){
            cin >> h_m_s;
            time_s = HourtoMin(h_m_s);
            if(i % 2 == 0) trains[i] = make_pair(time_s, 1);
            else trains[i] = make_pair(time_s, 0);
            // 到着したときは0、出発したときは1
        }
        sort(trains.begin(), trains.begin() + 2 * n);
        for(int i = 0; i < 2 * n; i++) cout << trains[i].first<< ' ' << trains[i].second << endl;
        int osaki_now_train = 0, need_train = 0;
        for(int i = 0; i < 2 * n; i++){
            if(trains[i].second == 1){
                if(osaki_now_train == 0) need_train++;
                else osaki_now_train--;
            } else if(trains[i].second == 0) osaki_now_train++;
        }
        cout << need_train << endl;
    }
    return 0;
}

int HourtoMin(string s)
{
    int ans = 0;
    for(int i = 0; i <= 6; i = i + 3){
        ans += ((s[i] - '0') * 10 + s[i + 1] - '0') * (int)pow(60, ((6 - i) / 3));
    }
    return ans;
}

C++: #include<bits/stdc++.h>
#define _ ios_base::sync_with_stdio(0);cin.tie(0);
#define REP(i,n) for(int i=0;i<(int)(n);i++)

using namespace std;

const int MAX_N=1000;

pair<int,int> p[MAX_N+1];

int main(){ _;
  int n,a=0,b=0,c=0,d=0,e=0,f=0;
  while(scanf("%d",&n),n!=0){
    REP(i,n){
      scanf("%02d:%02d:%02d %02d:%02d:%02d",&a,&b,&c,&d,&e,&f);
      p[i]=make_pair(a*3600+b*60+c,d*3600+e*60+f);
    }
    priority_queue<int,vector<int>,greater<int> > que;
    int maxTrain=0;
    sort(p,p+n);
    REP(i,n){
      while(!que.empty()&&que.top()<=p[i].first)
	que.pop();
      que.push(p[i].second);
      maxTrain=max(maxTrain,(int)que.size());
    }
    cout<<maxTrain<<endl;
  }
}

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

int main(){
    vector< vector<int> > trains;
    int n,i,j,k,f,t,h,m,s,flg;
    vector<int> buf(86401,0);
    while(1){
        scanf("%d",&n);
        if(!n){break;}
        for(i=0;i<n;i++){
            scanf("%d:%d:%d",&h,&m,&s);
            f=h*3600+m*60+s;
            scanf("%d:%d:%d",&h,&m,&s);
            t=h*3600+m*60+s;
            if(trains.empty()){
                fill(buf.begin()+f,buf.begin()+t,1);
                //for(j=f;j<=t;j++){buf[i]=1;}
                trains.push_back(buf);
            }
            else{
                for(auto itr=trains.begin();itr!=trains.end();itr++){
                    flg=0;
                    for(j=f+1;j<t;j++){if((*itr)[j]){flg=1;break;}}
                    if(!flg){
                        for(j=f;j<=t;j++){(*itr)[j]=1;}
                        break;
                    }
                }
                if(flg){
                    //for(j=f;j<=t;j++){buf[j]=1;}
                    fill(buf.begin()+f,buf.begin()+t,1);
                    trains.push_back(buf);
                }
            }
            fill(buf.begin(),buf.end(),0);
        }
        printf("%lu\n",trains.size());
        trains.clear();
        trains.shrink_to_fit();
    }
    return 0;
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

#define rep(i, n) for(int i=0; i<(n); ++i)
#define all(c) (c).begin(), (c).end()

template<typename T> inline void chmax(T& t, T f){if(t < f)t = f;}

vector<string> split(const string& input, char delimiter){
    istringstream stream(input);
    string field;
    vector<string> result;
    while(getline(stream, field, delimiter))result.push_back(field);
    return result;
}

int main(){
    int n;
    while(cin >> n, n){
        typedef pair<vector<string>, vector<string> > Time;
        vector<Time> table;
        rep(i, n){
            string s, t;
            cin >> s >> t;
            table.emplace_back(split(s, ':'), split(t, ':'));
        }
        sort(all(table));
        int ans = 1;
        rep(i, n){
            chmax(ans, 1 + (int)count_if(table.begin(), table.begin() + i,
                        [&](Time& t){return table[i].first < t.second;}));
        }
        cout << ans << '\n';
    }
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <cstdio>
using namespace std;
#define rep(i,a) for(int i = 0 ; i < a ; i ++)
int main(void){
  int n;
  while(cin>>n,n){
    vector<int> ary(24*60*60,0);
    char b[9],e[9];
    while(n--){
      cin>>b>>e;
      int h,m,s;
      sscanf(b,"%d:%d:%d",&h,&m,&s);
      int start = ((h * 60) + m) * 60 + s; 
      sscanf(e,"%d:%d:%d",&h,&m,&s);
      int finish = ((h * 60) + m) * 60 + s; 
      for(int i = start ; i < finish ; i ++)ary[i]++;
    }
    int ret = -1;
    for(int i = 0 ; i < ary.size() ; i ++)ret = max(ret,ary[i]);
    cout<<ret<<endl;
  }
}