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;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int INF = 1e9;
const ll LINF = 1e18;
inline ll gcd(ll a, ll b) { return b ? gcd(b, a%b) : a; }
inline ll lcm(ll a, ll b) { return a / gcd(a, b)*b; }
template<class S,class T> ostream& operator << (ostream& out,const pair<S,T>& o){ out << "(" << o.first << "," << o.second << ")"; return out; }
template<class T> ostream& operator << (ostream& out,const vector<T> V){ for(int i = 0; i < V.size(); i++){ out << V[i]; if(i!=V.size()-1) out << " ";} return out; }
template<class T> ostream& operator << (ostream& out,const vector<vector<T> > Mat){ for(int i = 0; i < Mat.size(); i++) { if(i != 0) out << endl; out << Mat[i];} return out; }
template<class S,class T> ostream& operator << (ostream& out,const map<S,T> mp){ out << "{ "; for(auto it = mp.begin(); it != mp.end(); it++){ out << it->first << ":" << it->second; if(mp.size()-1 != distance(mp.begin(),it)) out << ", "; } out << " }"; return out; }

/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */

template<class Type>
Type solve(Type res = Type()){
    int n;
    while(cin >> n){
        if(n == 0) break;
        vector<pii> T(n);
        for(int i = 0; i < n;i++){
            int h1,m1,s1,h2,m2,s2; char c;
            cin >> h1 >> c >> m1 >> c >> s1 >> h2 >> c >> m2 >> c >> s2;
            T[i].first = h1*3600 + m1*60 + s1;
            T[i].second = h2*3600 + m2*60 + s2;
        }
        sort(T.begin(),T.end());
        vector<int> train(48*3600+5);
        for(int i = 0; i < n;i++){
            int s,t; tie(s,t) = T[i];
            train[2*s] += 1;
            train[2*t] += -1;
        }
        for(int i = 1; i <= 48*3600;i++){
            train[i] += train[i-1];
        }
        cout << *max_element(train.begin(),train.end()) << endl;
    }
    
    return res;
}
int main(void) {
    cin.tie(0); ios_base::sync_with_stdio(false);
    solve<ll>();
    //cout << fixed << setprecision(15) << solve<ll>() << endl;
    return 0;
}

C++: /*** ??§?´? ***/

#include <bits/stdc++.h>
using namespace std;

int main(){
	int n;
	int i, j;
	int hh, mm, ss;
	int time[100000], count;
	
	cin >> n;
	while(n!=0){
		for(i=0; i<100000; ++i) time[i]=0;
		
		for(i=0; i<n; ++i){
			scanf("%d:%d:%d", &hh, &mm, &ss);
			//cin >> hh >>":" >> mm >> ":" >> ss;
			time[ss+60*mm+3600*hh]++;
			scanf("%d:%d:%d", &hh, &mm, &ss);
			//cin >> hh >>":" >> mm >> ":" >> ss;
			time[ss+60*mm+3600*hh]--;
		}
		
		count=0;
		for(i=0; i<100000; ++i){
			if(i>0) time[i]+=time[i-1];
			count = max(count, time[i]);
		}
		cout << count << endl;
		cin >> n;
	}
	return 0;
}

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

int convert(string s){
	int h=(s[0]-'0')*10+(s[1]-'0');
	int m=(s[3]-'0')*10+(s[4]-'0');
	int t=(s[6]-'0')*10+(s[7]-'0');
	return h*3600+m*60+t;
}

class range{
public:
	int left,right;
	range(int left,int right):left(left),right(right){}
	range(){};
};

bool is_connect(range a,range b){
	if(a.right<=b.left || b.right<=a.left) return false;
	return true;
}


int main()
{
	int n;
	while(cin>> n && n!=0){
		vector<range> V(n);
		for(int i=0;i<n;i++){
			string s,t;cin>>s>>t;
			V[i].left=convert(s);
			V[i].right=convert(t);
		}


		int ans=0;
		for(int i=0;i<n;i++){
			int count=1;
			for(int j=0;j<n;j++){
				if(i==j) continue;
				if(is_connect(V[i],V[j])) count++;
			}
			ans=max(ans,count);
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: #[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::Read;
#[allow(dead_code)]
fn getline() -> String {
    let mut ret = String::new();
    std::io::stdin().read_line(&mut ret).ok().unwrap();
    ret
}
fn get_word() -> String {
    let mut stdin = std::io::stdin();
    let mut u8b: [u8; 1] = [0];
    loop {
        let mut buf: Vec<u8> = Vec::with_capacity(16);
        loop {
            let res = stdin.read(&mut u8b);
            if res.unwrap_or(0) == 0 || u8b[0] <= b' ' {
                break;
            } else {
                buf.push(u8b[0]);
            }
        }
        if buf.len() >= 1 {
            let ret = String::from_utf8(buf).unwrap();
            return ret;
        }
    }
}

#[allow(dead_code)]
fn get<T: std::str::FromStr>() -> T { get_word().parse().ok().unwrap() }

fn to_time(v: Vec<u8>) -> usize {
    let h: usize = (10 * (v[0] - 48) + v[1] - 48).into();
    let m: usize = (10 * (v[3] - 48) + v[4] - 48).into();
    let s: usize = (10 * (v[6] - 48) + v[7] - 48).into();
    3600 * h + 60 * m + s
}

fn solve() {
    loop {
        let n = get();
        if n == 0 { break; }
        const T: usize = 86400;
        let mut imos = [0; T];
        for _ in 0 .. n {
            let a = to_time(get_word().bytes().collect::<Vec<_>>());
            let b = to_time(get_word().bytes().collect::<Vec<_>>());
            imos[a] += 1;
            imos[b] -= 1;
        }
        for i in 0 .. T - 1 {
            imos[i + 1] += imos[i];
        }
        let ma = imos.iter().max().unwrap();
        println!("{}", ma);
    }
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}