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 <vector>
#include <algorith>
using namespace std;

int main (){
  int n;
  vector< pair<int,int> > tm;
  while(cin>>n && n){
    tm.clear();
    char ch1,ch2;
    int h,m,s;
    for(int i=0;i<n;i++){
      cin>>h>>ch1>>m>>ch2>>s;
      tm.push_back(make_pair(h*3600+m*60+s,1));
      cin>>h>>ch1>>m>>ch2>>s;
      tm.push_back(make_pair(h*3600+m*60+s,-1));
    }
    sort(tm.begin(),tm.end());
    int ans=0;
    int co=0;
    for(int i=0;i<(int)tm.size();i++){
      co+=tm[i].second;
      ans = max(co,ans);
    }
    cout<<ans<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)

void slove(int n){
	vector<int> v(86410);
	rep(i, 86410) v[i] = 0;//?????????
	rep(i, n){
		string s, e;
		cin >> s >> e;
		//?§???°?????????
		int start = 36000 * (s[0] - '0') + 3600 * (s[1] - '0') 
					+ 600 * (s[3] - '0') + 60 * (s[4] - '0')
					+ 10 * (s[6] - '0') + 1 * (s[7] - '0');
		int end = 36000 * (e[0] - '0') + 3600 * (e[1] - '0') 
					+ 600 * (e[3] - '0') + 60 * (e[4] - '0')
					+ 10 * (e[6] - '0') + 1 * (e[7] - '0') - 1;
		printf("%d %d\n", start, end);
		for (int j = start; j <= end ; ++j) v[j]++;//???????????????
	}
	sort(all(v));
	reverse(all(v));
	printf("%d\n", v[0]);
}
int main(void){
	rep(i, 1000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<utility>
#include<queue>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<map>
#include<complex>
#define INF 2147483647
#define llINF 9223372036854775807
#define pb push_back
#define mp make_pair 
#define F first
#define S second
#define ll long long

using namespace std;
int main(){
  int n;
  while(cin>>n,n){
    int ma=0;
    int time_table[30][65][65]={};
    for(int i=0;i<n;i++){
      int a,b,c;
      scanf("%d:%d:%d",&a,&b,&c);
      time_table[a][b][c]++;
      scanf("%d:%d:%d",&a,&b,&c);
      time_table[a][b][c]--;
    }
    int cnt=0;
    for(int i=0;i<=24;i++){
      for(int j=0;j<=60;j++){
	for(int k=0;k<=60;k++){
	  cnt+=time_table[i][j][k];
	  ma=max(ma,cnt);
	}
      }
    }
    cout<<ma<<endl;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define o(a) cout << a << endl
// #define int long long
#define fi first
#define se second
using namespace std;
typedef pair<int, int> P;

signed main(){
    int n;
    while(1){
        cin >> n;
        if(n == 0) break;
        int h, m, s, hh, mm, ss;
        int d[24 * 3600 + 100] = {};
        rep(i, 0, n){
            scanf("%d:%d:%d %d:%d:%d", &h, &m, &s, &hh, &mm, &ss);
            int st = h * 3600 + m * 60 + s;
            int ed = hh * 3600 + mm * 60 + ss;
            d[st]++; d[ed]--;
        }
        int MAX = 0;
        rep(i, 1, 24 * 3600 + 10){
            d[i] += d[i - 1];
            MAX = max(MAX, d[i]);
        }
        cout << MAX << endl;
    }
}