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++: #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define rep0(N) for (int COUNTER = 0; COUNTER < (int)(N); COUNTER++)
#define rep(i, N) for (int i = 0; i < (int)(N); i++)
#define rep1(i, N) for (int i = 0; i < (int)(N); i++)
#define rep2(i, START, GOAL) for (int i = (int)(START); i < (int)(GOAL); i++)
#define rep3(i, START, GOAL) for (int i = (int)(START); i > (int)(GOAL); i--)
#define ALL(CONTAINER) CONTAINER.begin(), CONTAINER.end()
#define rALL(CONTAINER) CONTAINER.rbegin(), CONTAINER.rend()
#define from1(CONTAINER) CONTAINER.begin() + 1, CONTAINER.end()
#define rfrom1(CONTAINER) CONTAINER.rbegin(), CONTAINER.rend() - 1
#define output(X) cout << X << "\n"
#define dberr(X) cerr << X << " "
#define dberrl(X) cerr << X << "\n"
#define db(X) cerr << #X << ":" << (X) << " "
#define dbl(X) cerr << #X << ":" << (X) << "\n"
#define db2(X, Y) cerr << #X << ":" << (X) << ", " << #Y << ":" << (Y) << " "
#define db2l(X, Y) cerr << #X << ":" << (X) << ", " << #Y << ":" << (Y) << "\n"
#define dbl2(X, Y) cerr << #X << ":" << (X) << "\n" << #Y << ":" << (Y) << "\n"
#define db3(X, Y, Z) cerr << #X << ":" << (X) << ", " << #Y << ":" << (Y) << " " << #Z << ":" << (Z) << " "
#define db3l(X, Y, Z) cerr << #X << ":" << (X) << ", " << #Y << ":" << (Y) << ", " << #Z << ":" << (Z) << "\n"
#define dbl3(X, Y, Z) cerr << #X << ":" << (X) << "\n" << #Y << ":" << (Y) << "\n" << #Z << ":" << (Z) << "\n"
#define dbp(PAIR) cerr << #PAIR << ":(" << PAIR.first << ", " << PAIR.second << ") "
#define dbpl(PAIR) cerr << #PAIR << ":(" << PAIR.first << ", " << PAIR.second << ")\n"
#define dbt3(TUPLE3) cerr << #TUPLE3 << ":(" << get<0>(TUPLE3) << ", " << get<1>(TUPLE3) << ", " << get<2>(TUPLE3) << ") "
#define dbt3l(TUPLE3) cerr << #TUPLE3 << ":(" << get<0>(TUPLE3) << ", " << get<1>(TUPLE3) << ", " << get<2>(TUPLE3) << ")\n"
#define dbt4(TUPLE4) cerr << #TUPLE4 << ":(" << get<0>(TUPLE4) << ", " << get<1>(TUPLE4) << ", " << get<2>(TUPLE4) << ", " << get<3>(TUPLE4) << ") "
#define dbt4l(TUPLE4) cerr << #TUPLE4 << ":(" << get<0>(TUPLE4) << ", " << get<1>(TUPLE4) << ", " << get<2>(TUPLE4) << ", " << get<3>(TUPLE4) << ")\n"
#define dbv(VEC) cerr << #VEC << ":{ "; for (auto ELEM : VEC) cerr << ELEM << ", "; cerr << "}\n"
#define dbvp(VP) cerr << #VP << ":{ "; for (auto PAIR : VP) cerr << "(" << PAIR.first << ", " << PAIR.second << "), "; cerr << "}\n"
#define dbvv(VV) cerr << #VV << ":{\n"; for (auto VEC : VV) { cerr << "{ "; for (auto ELEM : VEC) cerr << ELEM << ", "; cerr << "},\n"; } cerr << "}\n"
#define dbvvp(VVP) cerr << #VVP <<":{\n"; for (auto VP : VVP) { cerr << "{ "; for (auto PAIR : VP) { cerr << "(" << PAIR.first << ", " << PAIR.second << "), "; } cerr << "},\n"; } cerr << "}\n";
#define dbm(MAP) cerr << #MAP << ":{ "; for (auto PAIR : MAP) cerr << "(" << PAIR.first << ", " << PAIR.second << "), "; cerr << "}\n"
#define YN(f) cout << (f ? "YES" : "NO") << "\n"
#define Yn(f) cout << (f ? "Yes" : "No") << "\n"
#define yn(f) cout << (f ? "yes" : "no") << "\n"
using ll = long long;
using vi = vector<int>; using vl = vector<ll>; using vd = vector<double>; using vs = vector<string>; using vb = vector<bool>;
using vvi = vector<vi>; using vvl = vector<vl>; using vvd = vector<vd>; using vvb = vector<vb>;
using pii = pair<int, int>; using pil = pair<int, ll> ; using pli = pair<ll, int>; using pll = pair<ll, ll>; using pdd = pair<double, double>;
using vpii = vector<pii>; using vpll = vector<pll>; using vpdd = vector<pdd>;
using ti3 = tuple<int, int, int>; using tl3 = tuple<ll, ll, ll>; using td3 = tuple<double, double, double>;
using ti4 = tuple<int, int, int, int>; using tl4 = tuple<ll, ll, ll, ll>; using td4 = tuple<double, double, double, double>;
using mii = map<int, int>; using mil = map<int, ll>; using mli = map<ll, int>; using mll = map<ll, ll>;
using si = set<int>; using sl = set<ll>;
// db

const int MAX = 24 * 60 * 60;

int second(string S) {
	int h = stoi(S.substr(0, 2));
	int m = stoi(S.substr(3, 2));
	int s = stoi(S.substr(6, 2));
	return h * 60 * 60 + m * 60 + s;	
}

void solve(int n) {
	vi a(MAX);
	rep0(n) {
		string str1, str2; cin >> str1 >> str2;
		int l = second(str1), r = second(str2);
		// db2l(l, r);
		a[l]++; a[r]--;
	}
	// dbv(a);
	rep2(i, 1, MAX) a[i] += a[i - 1];
	// dbv(a);
	output(*max_element(ALL(a)));	
}

int main() {
	while (true) {
		int n; cin >> n;
		if (n) solve(n);
		else break;		
	}
}

C++: #include <iostream>
#include <cstdio>
#include <map>
using namespace std;
int main() {
	int n;
	std::map<int, int> tv;
	for (;;) {
		cin >> n;
		if (!n) break;
		for (int i = 0; i < n; ++i) {
			int h, m, s1, s2;
			scanf("%2d:%2d%:%2d", &h, &m, &s1);
			m += h * 60;
			s1 += m * 60;
			scanf("%2d:%2d:%2d", &h, &m, &s2);
			m += h * 60;
			s2 += m * 60;
			++tv[s1];
			--tv[s2];
		}
		int c = 0, max = 0;
		for (auto i : tv) {
			c += i.second;
			if (max < c) max = c;
		}
		std::cout << max << std::endl;
	}
	return 0;
}