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 <string>
using namespace std;


#define M  24*60*60
int table[M];


int main(){
  int n;
  int h,m,sec;
  string str;
  while(cin >> n, n){

    for(int i = 0; i < n; i++){
      cin >> str;
      scanf("%d:%d:%d", &h,&m,&sec);
      int s = h*60*60 + m*60 + sec;
      table[s]++;
      scanf("%d:%d:%d", &h,&m,&s);
      int e = h*60*60 + m*60 + s;
      table[e]--;
    }
    for(int i = 1; i < M; i++){
      table[i] += table[i-1];
    }
    int max = 0;
    for(int i = 0; i < M; i++){
      if(max < table[i]) max = table[i];
    }
    cout << max << endl;
  }
}

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

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

const int H = 60 * 60, M = 60, CHAKU = 0, HATU = 1;

typedef pair<int, int> pp;

int main()
{
    int n;
    while(cin >> n && n)
    {
        int ans = 0, h, m, s;
        char t;
        vector<pp> tr;
        REP(n)
        {
            cin >> h >> t >> m >> t >> s;
            tr.push_back(pp(h * H + m * M + s, HATU));
            cin >> h >> t >> m >> t >> s;
            tr.push_back(pp(h * H + m * M + s, CHAKU));
        }
        sort(all(tr));

        int num = 0;
        REP(n)
            if(tr[i].second == CHAKU){ num--; ans = max(ans, num);}
            else { num++; ans = max(ans, num);}

        cout << ans << endl;
    }
    return 0;
}

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=10000;

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 <bits/stdc++.h>
using namespace std;
 
int main() {
  while(1) {
    int n;
    cin >> n;
    if(n == 0) break;
 
    int limit = 24*3600;
    int data[limit];
    for(int i = 0; i < limit; i++) {
      data[i] = 0;
    }
 
    for(int i = 0; i < n; i++) {
      int h, m, s;
      int ss, gs;
      scanf("%d:%d:%d", &h, &m, &s);
      ss = h*3600 + m*60 +s;
      scanf("%d:%d:%d", &h, &m, &s);
      gs = h*3600 + m*60 +s;
      for(int j = ss; j < gs; j++) {
        data[j]++;
      }
    }
 
    int max = -1;
    for(int i = 0; i < limit; i++) {
      if(data[i] > max) max = data[i];
    }
 
    cout << max << endl;
  }
  return 0;
}

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

int sec(int h,int m,int s){
	return (h*60+m)*60+s;
}
int main(){
	int n;
	while(cin>>n,n){
		map<int,int> mp;
		map<int,int>::iterator it;
		int ans=0;
		for(int i=0;i<n;i++){
			int h,m,s;
			scanf("%d:%d:%d",&h,&m,&s);
			++mp[sec(h,m,s)];
			scanf("%d:%d:%d",&h,&m,&s);
			--mp[sec(h,m,s)];
		}
		int use=0;
		for(it=mp.begin();it!=mp.end();++it){
			use += it->second;
			ans = max(ans,use);
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <set>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <string>
#include <map>
using namespace std;

int ChangeTimesFormat(string str){
    int h = atoi(str.substr(0,2).c_str());
    int m = atoi(str.substr(3,2).c_str());
    int s = atoi(str.substr(6,2).c_str());
    int time = h*60*60+m*60+s;
    return time;
}

int main(){
    int n;
    while(cin>>n&&n!=0){
        // ðkeyÆµÄA»ÌÉ­Ë·éñÔÌ,·éñÔÌð²×é
        map<int,pair<int,int> > m;
        for(int i = 0; i < n; i++){
            string from;
            string to;
            cin>>from>>to;
            int ft=ChangeTimesFormat(from);
            int tt=ChangeTimesFormat(to);
            m[ft].first++;
            m[tt].second++;
        }
        // ñÔÌÅå
        int maxLine=0;
        // »ÝcÁÄ¢éÌñÔÌ
        int cnt=0;
        // Ì¢Ô©çµÄ¢­
        for(map<int,pair<int,int> >::iterator it = m.begin(); it!=m.end(); it++){
            // ©¦ÁÄ«½ñÔðo^
            cnt+=it->second.second;
            // o­·éñÔÌÌûª½¢ÈçÎ
            if(cnt<it->second.first){
                maxLine+=it->second.first-cnt;
                cnt=0;
            }
            else{
                cnt-=it->second.first;
            }
        }
        cout<<maxLine<<endl;
    }
    return 0;
}