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;

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

int main() {
	int n;
	while (cin >> n, n) {
		deque<pair<int, int>> q, r;
		for (int i = 0; i < n; i++) {
			string s, t;
			cin >> s >> t;
			q.push_back(make_pair(f(s), f(t)));
		}
		sort(begin(q), end(q));
		int m = 1;
		auto l = q.front();
		q.pop_front();
		while (!q.empty()) {
			auto p = q.front();
			q.pop_front();
			if (l.second <= p.first) {
				l = p;
			} else {
				r.push_back(p);
			}
			if (q.empty() && !r.empty()) {
				m++;
				while (!r.empty()) {
					q.push_back(r.front());
					r.pop_front();
				}
				l = q.front();
				q.pop_front();
			}
		}
		cout << m << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<cstdio>
using namespace std;
int a[24 * 60 * 60+10];
int main() {
	long long a1, m1, a2, m2, a3, m3;
	int n;
	while (cin >> n&&n != 0) {
		int h1, m1, s1, h2, m2, s2;
		fill(a, a + 60 * 24 * 60+10, 0);
		int sum = 0;
		for (int i = 0; i<n; i++) {
			scanf_s("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
			if (a[h1 * 3600 + m1 * 60 + s1] == 0) {
				sum++;
				for (int i = 0; i<24 * 60 * 60+10; i++) a[i]++;
			}
			for (int i = h1 * 3600 + m1 * 60 + s1; i<h2 * 3600 + m2 * 60 + s2; i++) {
				a[i]--;
			}
			a[h2 * 3600 + m2 * 60 + s2]++;
		}
		cout << sum << endl;
	}
}

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

#ifdef LOCAL
#include "../dump.hpp"
#else
#define dump(...)
#endif

#define rep(i,n) for(ll i=0,i##_cond=(n);i<i##_cond;i++)
#define FOR(i,a,b) for(ll i=(a),i##_cond=(b);i<i##_cond;i++)
#define ROF(i,a,b) for(ll i=(a)-1,i##_cond=(b);i>=i##_cond;i--)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend() //sortで大きい順
#define UNIQUE(v) v.erase(unique(all(v)),v.end())
#define SUM(a) accumulate(all(a),0)
#define sz(x) ((ll)(x).size())
#define pb push_back
#define fst first
#define snd second
#define mp make_pair

typedef long long ll;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<ll,ll> pii;

const ll inf = 1ll<<62;
const ll mod = 1e9+7;

#define int ll

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

main()
{
  while(1){
    int n; cin >> n;
    if(n == 0) break;

    vi time(24*60*60);

    rep(i,n){
      string sts,gts; cin >> sts >> gts;
      int st = convert(sts), gt = convert(gts);
      time[st]++; time[gt]--;
      //dump(time[st],time[gt]);
    }

    rep(i,sz(time)-1) time[i+1] += time[i];

    cout << *max_element(all(time)) << endl;
  }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>

using namespace std;

typedef pair<int,int> P;
 
int main(){
    int n;
     
    while(cin >> n,n){
        vector<P> v;
        int sh,sm,ss,th,tm,ts,Max=0,Min = 99999,totals,totalt;
        for(int i = 0 ; i < n ; i++){
            scanf("%d:%d:%d" ,&sh , &sm , &ss);
            totals = sh*3600+sm*60+ss;
            v.push_back(P(totals,1));
            scanf("%d:%d:%d" ,&th , &tm , &ts);
            totalt = th*3600+tm*60+ts;
            v.push_back(P(totalt,-1));
        }
        sort(v.begin(),v.end());
     
        int ans = 0,tmp = 0;
        for(int i = 0 ; i < v.size() ; i++){
	    tmp += v[i].second;
	    ans = max(ans,tmp);
        }
        cout << ans << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
int main(){
  vector<int> st;
  vector<int> fi;
  int n,t;
  int c,m;
  string T;
  while(1){
    c=0;
    m=0;
    st.empty();
    fi.empty();
    //
    cin >> n;
    if(n==0)break;
    for(int i=0;i<n;i++){
      cin >> T;
      t=(T[0]-'0')*36000+(T[1]-'0')*3600+(T[3]-'0')*600+(T[4]-'0')*60+(T[6]-'0')*10+T[7]-'0';
      st.push_back(t);
      cin >> T;
      t=(T[0]-'0')*36000+(T[1]-'0')*3600+(T[3]-'0')*600+(T[4]-'0')*60+(T[6]-'0')*10+T[7]-'0';
      fi.push_back(t);
    }
    sort(st.begin(),st.end());
    sort(fi.begin(),fi.end());
    int i1=0,i2=0;
    while(1){
      if(st[i1]<fi[i2]){
	i1++;
	c++;
	m=max(m,c);
	if(i1==n)break;
      }
      else{
	i2++;
	c--;
	if(i2==n)break;
      }
    }
    cout << m << endl;
  }
  return 0;
}

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() {
	ios::sync_with_stdio(false);

	while(true) {
		int n;
		cin >> 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);
		}
		cout << ans << endl;
	}

	return 0;
}