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<cstdio>
#include<string>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;
#define P pair<int,int>//出発、到着

vector<P>ta;
bool used[11000];
void init(string x,string y){
			int s,e;
	string a=x.substr(0,2),b=x.substr(3,2),c=x.substr(6,2);
	int aa=(a[0]-'0')*10+(a[1]-'0');
	int bb=(b[0]-'0')*10+(b[1]-'0');
	int cc=(c[0]-'0')*10+(c[1]-'0');
	s=aa*3600+bb*60+cc;
	 a=y.substr(0,2),b=y.substr(3,2),c=y.substr(6,2);
	 aa=(a[0]-'0')*10+(a[1]-'0');
	 bb=(b[0]-'0')*10+(b[1]-'0');
	cc=(c[0]-'0')*10+(c[1]-'0');
	e=aa*3600+bb*60+cc;
	P tmp=make_pair(s,e);
	ta.push_back(tmp);

}
bool ok(int n){
for(int i=0;i<n;i++)if(used[i]==0)return false;
return true;
}
int main(){
	int n;
	while(true){
	cin>>n;
	if(n==0)break;
	ta.clear();
for(int i=0;i<n;i++){
	string x,y;
	cin>>x>>y;
	init(x,y);
}
int ans=1;
fill(used,used+11000,false);
	//trueなら使ったってこと
	
	int now=0,j=0,b=9999999,next=0;
	while(ok(n)==false){
	//for(int i=0;i<n;i++)cout<<used[i]<<" ";cout<<endl;
	for(int i=0;i<n;i++){
	if(ta[i].first>=now&&used[i]==0&&b>ta[i].second){
	b=ta[i].second;
	j=i;
	}
	}
	
	next=ta[j].second;
	if(now!=next){
	now=next;
	used[j]=1;
	b=9999999;
	}
	else {
	ans++;
	now=0,next=0;
	b=9999999;
	}
}
	cout<<ans<<endl;
}
	return 0;
}

C++: #include <iostream>
#include <math.h>
#include <algorithm>
#include <string>

#define REP(i,n) for(int i=0; i<n; i++)
#define debug(x) cerr << __LINE__ << " : " << #x << " = " << (x) << endl;
 
#define mod 1000000007 //1e9+7(prime number)
#define INF 1000000000 //1e9
#define SIZE 86400	// 60*60*24

using namespace std;
typedef long long ll;

int main(){
	while(1){
		int n, data[SIZE], h, m, s, t, ans;
		
		cin >> n;
		if (n==0) break;
		REP(i,SIZE) data[i] = 0;
		ans = 0;
		
		REP(i,n){
			//debug(i);
			scanf("%d:%d:%d", &h, &m, &s);
			t = h*60*60 + m*60 + s;
			//debug(t);
			data[t]++;
			scanf("%d:%d:%d", &h, &m, &s);
			t = h*60*60 + m*60 + s;
			//debug(t);
			data[t]--;		
		}
		
		
		
		for (int i=1; i<SIZE; i++) data[i]+=data[i-1];
		
		REP(i,SIZE){
			if (ans<data[i]){
				ans = data[i];
			}
		}
			
		
		cout << ans << endl;
	}
	return 0;
}

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

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

C++: #include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define INF 1000000000
#define rep(i,a,b) for (int i=(a);i<(b);i++)
#define rev(i,a,b) for (int i=(a)-1;i>=b;i--)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef queue<int> qi;
typedef vector<int> vi;
typedef vector<string> vs;
int dx[4] = { 0, 1, 0, -1 };
int dy[4] = { 1, 0, -1, 0 };

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

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

		vector<pii> vp;
		rep(i,0,n) {
			int h,m,s;
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, 1));
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, -1));
		}

		sort(vp.begin(), vp.end());

		int ans = 0, tmp = 0;
		rep(i,0,vp.size()) {
			tmp += vp[i].second;
			ans = max(ans, tmp);
		}
		printf("%d\n", n);
	}

	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <algorithm>
#include <string>
using namespace std;

typedef pair<int,int> P;

int main(){
	int n;
	while( scanf("%d", &n), n ){
		priority_queue<P, vector<P>, greater<P> > q;
		
		for(int i=0 ; i < n ; i++ ){
			int h1, m1, s1, h2, m2, s2;
			scanf("%d:%d:%d", &h1, &m1, &s1);
			scanf("%d:%d:%d", &h2, &m2, &s2);
			int t1 = h1 * 60 * 60 + m1 * 60 + s1;
			int t2 = h2 * 60 * 60 + m2 * 60 + s2;
			q.push( P(t1, +1) );
			q.push( P(t2, -1) );
		}
		int ans = 0, cnt = 0;
		while( !q.empty() ){
			P p = q.top(); q.pop();
			if( p.second == -1 ){
				cnt--;
			}else{
				cnt++;
				ans = max(ans, cnt);
			}
		}
		printf("%d\n", ans);
	}
}