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 <vector>
#define REP(i,n) for(int i=0;i<(n);i++)
using namespace std;
int main()
{
  while(1){
    int n;
    scanf("%d", &n);
    if(n == 0) break;
    int ans = 1;
    int t = 1;
    vector<int> time;
    REP(i,n){
      int h, m, s;
      scanf("%d:%d:%d", &h, &m, &s);
      int ts = h*3600 + m*60 + s;
      if(!time.empty())
        REP(j,(int)time.size())
          if(time[j] <= ts){
            t++;
            time.erase(time.begin()+j);
          }
      scanf("%d:%d:%d", &h, &m, &s);
      int te = h*3600 + m*60 + s;
      if(t > 0){
        t--;
        time.push_back(te);
      }else{
        ans++;
        time.push_back(te);
      }
    }
    cout << ans << endl;
  }
}

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<char> vc;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<pii> vpii;
typedef vector<vi> vvi;
typedef vector<vb> vvb;
typedef vector<vpii> vvpii;
const int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
const int MOD = 1000000007;
const double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
bool odd(const int &n) { return n & 1; }
bool even(const int &n) { return !odd(n); }
void solve();
main { solve(); return 0; }
// clang-format on

void solve() {
  int n;
  while (cin >> n, n) {
    vi v(86400);
    rep(i, n) {
      int h, m, d;
      char gomi;
      cin >> h >> gomi >> m >> gomi >> d;
      int l = h * 3600 + m * 60 + d;
      cin >> h >> gomi >> m >> gomi >> d;
      int r = h * 3600 + m * 60 + d;
      v[l]++;
      v[r]--;
    }
    loop(i, 1, 86400) v[i] += v[i - 1];
    int c = 0;
    rep(i, 86400) cmax(c, v[i]);
    cout << c << endl;
  }
}

C++: #include "bits/stdc++.h"
using namespace std;

#define ASC(vec) vec.begin(), vec.end()		// 昇順ソート 例：sort(ASC(vec));
#define DESC(vec) vec.rbegin(), vec.rend()	// 降順ソート 例:sort(DESC(vec));
#define rep(i, n) for(int i = 0; i < (n); i++)
#define Rep(i, n) for(int i = 1; i < n; i++)

const int mod = 1000000007;
const int inf = (1 << 21);
const long long INF = 1LL << 60;

using ii = pair<int, int>;
using ll = long long;
using vi = vector<int>;
using vd = vector<double>;
using vb = vector<bool>;
using vl = vector<ll>;
using vs = vector<string>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<ll>>;
using vvb = vector<vector<bool>>;
using vii = vector<pair<int, int>>;

template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
ll LCM(ll a, ll b) { return (a * b) / GCD(a, b); }
int round_int(int a, int b) { return (a + (b - 1)) / b; }

constexpr array<int, 9> dx = { 0, 1, 0, -1, -1, 1, 1, -1, 0 };
constexpr array<int, 9> dy = { 1, 0, -1, 0, 1, 1, -1, -1, 0 };

// ──────────────────────────────────────────────────────────────────

int main() {
	int t = 24 * 3600 + 59 * 60 + 59;

	while (true) {
		int n;
		cin >> n;

		if (!n) break;
		vi time(t + 1);

		rep(i, n) {
			int sh, sm, ss, eh, em, es;

			scanf("%d:%d:%d", &sh, &sm, &ss);
			scanf("%d:%d:%d", &eh, &em, &es);

			time[sh * 3600 + sm * 60 + ss]++;
			time[eh * 3600 + em * 60 + es]--;
		}
		int ans = 0;
		rep(i, t) {
			time[i + 1] += time[i];
			chmax(ans, time[i + 1]);
		}
		cout << ans << endl;

	}
}

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

int v[20000];
int b[10000], e[10000];
int p[20000];
bool f[20000];

int main()
{
	int n;
	while (scanf("%d", &n), n){
		memset(f, false, sizeof(f));
		
		for (int i = 0; i < n; i++){
			int h, m, s;
			scanf("%d:%d:%d", &h, &m, &s);
			b[i] = h * 60 * 60 + m * 60 + s;
			scanf("%d:%d:%d", &h, &m, &s);
			e[i] = h * 60 * 60 + m * 60 + s;
			
			v[i * 2] = b[i];
			v[i * 2 + 1] = e[i];
		}
		
		sort(v, v + 2 * n);
		
		for (int i = 0; i < n; i++){
			b[i] = lower_bound(v, v + 2 * n, b[i]) - v;
			e[i] = lower_bound(v, v + 2 * n, e[i]) - v;
			p[b[i]] = e[i];
		}
		
		int last = 0;
		int res = 1;
		for (int i = 0; i < 2 * n; i++){
			if (f[i]) continue;
			f[i] = f[p[i]] = true;
			res += (i < last);
			last = max(last, p[i]);
		}
		
		printf("%d\n", res);
	}
	
	return 0;
}