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 <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
#include <utility>
#include <functional>
#include <sstream>
#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <climits>

using namespace std;

inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str();}

typedef vector<int> vi;
typedef vector<vi>  vvi;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef long long ll;

#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EACH(t,i,c) for(t::iretator i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

const double EPS = 1e-10;

int main(){
    int n;
    const int TIME = 86400;
     
    while( scanf("%d",&n) , n ){
        int timeTable[TIME] = {};
        for(int i=0 ; i<n ; ++i ){
            int h1,m1,s1,h2,m2,s2,start,end;
            scanf("%d:%d:%d %d:%d:%d", &h1 , &m1 , &s1 , &h2 , &m2 , &s2 );
            start = s1 + m1*60 + h1*60*60;
            end   = s2 + m2*60 + h2*60*60 -1;
            for(int j = start ; j <= end ; ++j ){
                timeTable[j]++;
            }
        }
        int ans = 0;
        for(int i=0 ; i<TIME ; ++i ){
            ans = max( ans , timeTable[i] );
        }
        printf("%d\n", ans );
         
    }
}

C++: #include<map>
#include<set>
#include<list>
#include<cmath>
#include<queue>
#include<stack>
#include<cstdio>
#include<string>
#include<vector>
#include<complex>
#include<cstdlib>
#include<cstring>
#include<numeric>
#include<sstream>
#include<iostream>
#include<algorithm>
#include<functional>

#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)

using namespace std;

typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;

const int INF=1<<29;
const double EPS=1e-9;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
int n;
int sch[86410];//秒単位に変換
int main(){
	while(cin>>n,n){
		for(int i = 0;i <=86410;i++){
			sch[i] = 0;
		}
		for(int i = 0;i < n;i++){
			string str;
			int h,m,s;
			cin>>str;
			h = ((str[0]-'0')*10+(str[1]-'0'))*60*60;
			m =((str[3]-'0')*10 +(str[4]-'0'))*60;
			s =(str[6]-'0')*10+(str[7]-'0');
			int dep = h+m+s;
			cin>>str;
			h = ((str[0]-'0')*10+(str[1]-'0'))*60*60;
			m =((str[3]-'0')*10 +(str[4]-'0'))*60;
			s =(str[6]-'0')*10+(str[7]-'0');
			int arr = h+m+s;
			for(int i =dep;i <arr;i++){
				sch[i]+=1;
			}
		}
		int ans = 0;
		for(int i =0;i <=86410;i++){
			ans =max(ans,sch[i]);
		}
		cout <<ans<<endl;
	}
	return 0;
}

C++: #include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
typedef pair<int, int> P;
typedef pair<int, P> PP;
int main()
{
  int n;
  while(cin>>n,n) {
    priority_queue<PP, vector<PP>, greater<PP> > Q;
    int ans = 0;
    FOR(i,0,n) {
      int h1, m1, s1;
      int h2, m2, s2;
      scanf("%d:%d:%d %d:%d:%d",&h1,&m1,&s1,&h2,&m2,&s2);
      if(Q.empty()) {
        ans++;
        Q.push(PP(h2, P(m2, s2)));
      } else {
        PP pp = Q.top();
        int h = pp.first;
        int m = pp.second.first;
        int s = pp.second.second;
        if(h1 == h) {
          if(m1 == m) {
            // ?????????
            if(s1 >= s) {
              Q.pop();
              Q.push(PP(h2, P(m2, s2)));
            } else {
              ans++;
              Q.push(PP(h2, P(m2, s2)));
            }
          } else {
            // ?????????
            if(m1 >= m) {
              Q.pop();
              Q.push(PP(h2, P(m2, s2)));
            } else {
              ans++;
              Q.push(PP(h2, P(m2, s2)));
            }
          }
        } else {
          if(h1 >= h) {
            Q.pop();
            Q.push(PP(h2, P(m2, s2)));
          } else {
            ans++;
            Q.push(PP(h2, P(m2, s2)));
          }
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}

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

using namespace std;
const int MAX = 100000;
typedef pair<int,int> P;
int ans[MAX];

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

void init(){
  fill(ans,ans+MAX,0);
}

int main(){
  int n;
  while(cin >> n && n){
    init();
    for(int i = 0; i < n; i++){
      int hh,ss,mm;
      int hh2,ss2,mm2;
      scanf("%d:%d:%d",&hh,&ss,&mm);
      scanf("%d:%d:%d",&hh2,&ss2,&mm2);
      int from = ToS(hh,mm,ss);
      int to = ToS(hh2,mm2,ss2);
      for(int i = from; i < to; i++)
	ans[i]++;
    }
    
    int out = 0;
    for(int i = 0; i < MAX; i++)
      out = max(out,ans[i]);

    cout << out << endl;

  }
  return 0;
}