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++:  #define _USE_MATH_DEFINES
 #define INF 100000000
 #include <iostream>
 #include <cstdio>
 #include <sstream>
 #include <cmath>
 #include <cstdlib>
 #include <algorithm>
 #include <queue>
 #include <stack>
 #include <limits>
 #include <map>
 #include <string>
 #include <cstring>
 #include <set>
 #include <deque>
 #include <bitset>
 #include <list>

 using namespace std;

 typedef long long ll;
 typedef pair <int,int> P;

 static const double EPS = 1e-8;

int hour2second(int h,int m,int s){
  return h*60*60+m*60+s;
}

class Time{
public:
  int first;
  int last;
  Time(int a,int b) : first(a),last(b){}
  bool operator<(const Time& t1) const{
    return first < t1.first;
  }
};

int main(){
   int n;
   while(~scanf("%d",&n)){
     if(n==0) break;

     vector<Time> times;
     for(int i=0;i<n;i++){
       //hh:mm:ss hh:mm:ss 
       int hh[2],mm[2],ss[2];
       scanf("%d:%d:%d %d:%d:%d",
	     hh,mm,ss,hh+1,mm+1,ss+1);
       int first_second = hour2second(hh[0],mm[0],ss[0]);
       int last_second = hour2second(hh[1],mm[1],ss[1]);
       times.push_back(Time(first_second,last_second));
     }
     sort(times.begin(),times.end());
     int res = 1;

     for(int i=0;i<times.size();){
       int tmp = 1;
       // printf("i:%d\n",i);
       bool is_end = true;
       for(int j=i+1;j<times.size();){
	 bool is_end = false;
	 if(times[j].first < times[i].last){
	   j++; tmp++;
	   res = max(tmp,res);
	   // printf("i:%d j:%d\n",i,j);
	 }
	 else{
	   i=j;
	   break;
	 }
       }
       if(is_end) i++;
     }
     printf("%d\n",res);
   }
}

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

int main(){
    int n;
    string S, T;
    int i, ans;
    int daytime[86402];
    cin >> n;
    while(n>0){
        fill(daytime,daytime+86402,0);
        for(i=0; i<n; i++){
            cin >> S >> T;
            daytime[((S[0]-'0')*10+(S[1]-'0'))*3600+((S[3]-'0')*10+(S[4]-'0'))*60+((S[6]-'0')*10+(S[7]-'0'))]++;
            daytime[((T[0]-'0')*10+(T[1]-'0'))*3600+((T[3]-'0')*10+(T[4]-'0'))*60+((T[6]-'0')*10+(T[7]-'0'))]--;
        }
        for(i=1; i<=86400; i++){
            daytime[i] += daytime[i-1];
        }
        ans=0;
        for(i=0; i<=86400; i++){
            ans = max(ans,daytime[i]);
        }
        cout << ans << endl;
        cin >> n;
    }
    return 0;
}

C++: #include <iostream>
#include <map>
#include <algorithm>

using namespace std;

int main(){
    int n;
    while(cin >> n && n){
        multimap<int,bool> m;
        int ret=0,hh,mm,ss,tmp;

        for(int i=0;i<n;i++){
            for(int j=0;j<2;j++){
                cin >> hh;
                cin.ignore();
                cin >> mm;
                cin.ignore();
                cin >> ss;
                tmp = hh * 3600 + mm * 60 + ss;
                if(j == 0){
                    m.insert(make_pair(tmp, true));
                }else{
                    m.insert(make_pair(tmp, false));
                }
            }
        }
        multimap<int,bool>::iterator it = m.begin(),jt;
        tmp = 0;
        while(it != m.end()){
            if((*it).second){
                tmp++;
            }else{
                tmp--;
            }
            jt = it;
            ++jt;
            if(jt == m.end() || (*jt).first != (*it).first){
                ret = max(ret, tmp);
            }
            ++it;
        }
        cout << ret << endl;
    }
}

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]);
    }
    cout << ans << endl;
}

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

C++: #include<bits/stdc++.h>
using namespace std;
int main(){
	int n;
	while(cin>>n,n){
		int t[30000];
		int sgn[30000];
		for(int i = 0;i < n;i++){
			int h,m,s;
			scanf("%02d:%02d:%02d",&h,&m,&s);
			t[2 * i] = h*60*60+m*60+s;
			sgn[2 * i] = 1;
			scanf("%02d:%02d:%02d",&h,&m,&s);
			t[2 * i + 1] = h*60*60+m*60+s;
			sgn[2 * i + 1] = -1;
		}
		for(int i = 0;i < 2*n;i++){
			for(int j = i+1;j < 2*n;j++){
				if(t[i] == t[j] ? sgn[i] > sgn[j] : t[i] > t[j]){
					swap(t[i],t[j]);
					swap(sgn[i],sgn[j]);
				}
			}
		}
		int cnt = 0;
		int ma = 0;
		for(int i = 0;i < 2*n;i++){
			//cout<<t[i]<<" "<<sgn[i]<<endl;
			cnt += sgn[i];
			ma = max(cnt,ma);
		}
		cout<<ma<<endl;
	}
}

C++: #include <stdio.h>
#include <iostream>
using namespace std;

int main() {
  int n;
  int h1, m1, s1;
  int h2, m2, s2;

  while(cin >> n, n!=0){
    int res = 0;
    signed int time[24*3600+60*60+60] = {0};
    for(int i = 0; i < n; i++) {
      scanf("%d:%d:%d", &h1, &m1, &s1);
      scanf("%d:%d:%d", &h2, &m2, &s2);
      time[h1*3600+m1*60+s1]++;
      time[h2*3600+m2*60+s2]--;
    }

    for(int i = 0; i < 24*3600+60*60+60; i++) {
      time[i+1]+=time[i];
      if(res < time[i+1])
        res = time[i+1];
    }
    cout << res << endl;
  }
  return 0;
}