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<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define fi first
#define se second
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9;
const ll INF=4e18;
const ll dy[4]={1,0,-1,0};
const ll dx[4]={0,-1,0,1};
int main(){
    while(true){
        int N;cin>>N;if(!N)break;
        vl a(100000);
        rep(i,N){
            string S;cin>>S;
            int h=(S[0]-'0')*10+(S[1]-'0'),m=(S[3]-'0')*10+(S[4]-'0'),s=(S[6]-'0')*10+(S[7]-'0');
            a[(h*60+m)*60+s]++;
            cin>>S;
            h=(S[0]-'0')*10+(S[1]-'0'),m=(S[3]-'0')*10+(S[4]-'0'),s=(S[6]-'0')*10+(S[7]-'0');
            a[(h*60+m)*60+s]--;
        }
        rep(i,90000){
            a[i+1]+=a[i];
        }
        ll ans=0;
        rep(i,100000)ans=max(ans,a[i]);
        cout<<ans<<endl;
    }
    return 0;
}

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

using namespace std;

int main(){
	int n;
	while(scanf("%d",&n),n){
		array<int,24*60*60> time;
		for(int i=0;i<24*60*60;i++) time[i] = 0;
		for(int i=0;i<n;i++){
			int h1,m1,s1,h2,m2,s2;
			scanf("%d:%d:%d %d:%d:%d",&h1,&m1,&s1,&h2,&m2,&s2);
			
			int start = h1*60*60 + m1*60 + s1;
			int end = h2*60*60 + m2*60 + s2;
			for(int j=start;j<end;j++) time[j]++;
		}
		int ret = 0;
		for(int i=0;i<24*60*60;i++){
			ret = max(ret,time[i]);
		}
		printf("%d\n",ret);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
int n;

int cti(char c) { return (c - '0'); }

int encode(string s) {
	int H = 10 * cti(s[0]) + cti(s[1]);
	int M = 10 * cti(s[3]) + cti(s[4]);
	int S = 10 * cti(s[6]) + cti(s[7]);
	return 3600 * H + 60 * M + S;
}

int main() {
	while (cin >> n, n) {
		priority_queue<pii, vector<pii>, greater<pii> > q;
		for (int i = 0; i < n; i++) {
			string in, out; cin >> in >> out;
			q.push(make_pair(encode(in), 1));
			q.push(make_pair(encode(out), -1));
		}
		
		int ans = 0, cnt = 0;
		while (!q.empty()) {
			int t = q.top().second; q.pop();
			cnt += t;
			ans = max(ans, cnt);
		}
		
		cout << ans << endl;
	}
	
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<queue>
#include<deque>
#include<map>
#include<bitset>
using namespace std;

typedef long long ll;
#define rep(i, n) for(int i = 0;i < (n);i++)
#define repr(i, n) for(int i = (n);i >= 0;i--)
#define repf(i, m, n) for(int i = (m);i < (n);i++)
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1;} return 0;}
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1;} return 0;}
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
//////////////////////////////////////////////////


int main() {
    while (1) {
        int n, a, b;
        string s;
        cin >> n;
        if (n == 0) break;
        vector<int> sum(1e5);
        rep(i,n) {
            cin >> s;
            a = 0, b = 0;
            a += ((s[0]-'0')*10+(s[1]-'0')) * 3600;
            a += ((s[3]-'0')*10+(s[4]-'0')) * 60;
            a += (s[6]-'0')*10+(s[7]-'0');
            cin >> s;
            b += ((s[0]-'0')*10+(s[1]-'0')) * 3600;
            b += ((s[3]-'0')*10+(s[4]-'0')) * 60;
            b += (s[6]-'0')*10+(s[7]-'0');
            // cout << a << " " << b << endl;
            sum[a]++; sum[b]--;
        }
        int ans = 0, now = 0;
        rep(i,1e5) {
            now += sum[i];
            chmax(ans, now);
        }
        cout << ans << endl;
    }
    return 0;
}