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++: //Name: Osaki
//Level: 2
//Category: 区間,区間の重なり,累積和
//Note: 

/**
 * 少し問題文がわかりづらいが、与えられた区間が最も多く重なっているとき、いくつの区間が重なっているかを答える問題。
 * 1日の1秒を1要素に対応させた配列を用意して、各区間について出発時に+1、到着時に-1を書き込み、累積和を取った時に
 * 配列内の最大値が求める答えである。
 *
 * オーダーは O(N + S)。
 * ただしSは1日の秒数で、S=86400。
 */
#include <iostream>
#include <algorithm>
#include <array>

using namespace std;

int read_time() {
    int h, m, s;
    cin >> h;
    cin.ignore();
    cin >> m;
    cin.ignore();
    cin >> s;
    return h*3600 + m*60 + s;
}

bool solve(bool first) {
    int N;
    if(!(cin >> N)) return false;
    if(!N) return false;

    static array<int,86400> v;
    fill(begin(v), end(v), 0);
    for(int i = 0; i < N; ++i) {
        const int s = read_time();
        const int t = read_time();
        v[s]++;
        v[t]--;
    }
    int ans = 0;
    for(int i = 1; i < 86400; ++i) {
        v[i] += v[i-1];
        ans = max(ans, v[i]);
    }
    cout << ans << endl;
    return true;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    cout.setf(ios::fixed);
    cout.precision(10);

    bool first = true;
    while(solve(first)) {
        first = false;
    }
    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 t[90000];

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	while(true) {
		int n;
		cin >> n;
		if(!n) break;

		rep(i,0,90000) t[i] = 0;
		rep(i,0,n) {
			int h,m,s;
			scanf("%d:%d:%d", &h, &m, &s);
			t[h*3600 + m*60 + s]++;
			scanf("%d:%d:%d", &h, &m, &s);
			t[h*3600 + m*60 + s]--;
		}

		int ans = -1, tmp = 0;
		rep(i,0,90000) {
			tmp += t[i];
			ans = max(ans, tmp);
		}
		cout << ans << endl;
	}
	return 0;
}

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

#define MAX 1000

int to_int(char c) {
    return 9 - (int)('9' - c);
}

int to_num(string s) {
    int t = 0;
    //cout << "{" << s[0] << "," << to_int(s[0]) << "}" << endl;
    t += (to_int(s[0]) * 10 + to_int(s[1])) * 100 * 100;
    t += (to_int(s[3]) * 10 + to_int(s[4])) * 100;
    t += (to_int(s[6]) * 10 + to_int(s[7]));
    return t;
}

int enable_train_index(int list[], int now_list_max, int t1) {
    sort(list, list+now_list_max);
    for(int i=now_list_max-1; i>=0; i--) {
        if (list[i] == -1) { continue; }
        if (list[i] <= t1) { return i; }
    }
    return -1;
}

int main(void) {
    int n;
    string s;
    while (cin >> n, n) {
        int list[MAX];
        int now_list_max = 0;
        int train_num = 0;
        for(int i=0; i<n; i++) {
            list[i] = -1;
        }
        for(int i=0; i<n; i++) {
            cin >> s;
            int t1 = to_num(s);
            cin >> s;
            int t2 = to_num(s);
            int index = enable_train_index(list, now_list_max, t1);
            //cout << "[" << t1 << "," << t2 << "]" << endl;
            if (index != -1) {
                list[index] = -1;
            } else {
                train_num++;
            }
            list[now_list_max] = t2;
            now_list_max++;
        }
        cout << train_num;
        cout << endl;
    }
    return 0;
}

C++: #include<cstdio>
#include<functional>
#include<algorithm>
using namespace std;
int a[3600*24];
int main(void)
{
	int i,n,mx,x,h,m,s,t1,t2;
	while(1)	{
		scanf("%d",&n);
		if(n==0)	break;
//		printf("%d\n",n);
		for(i=0;i<3600*24;i++)	a[i]=0;
		for(i=0;i<n;i++)	{
			scanf("%d:%d:%d",&h,&m,&s);
			t1=h*3600+m*60+s;
			scanf("%d:%d:%d",&h,&m,&s);
			t2=h*3600+m*60+s;	
			a[t1]++;	a[t2]--;	
		}

		x=0;	mx=0;
		for(i=0;i<3600*24;i++)	{
			x+=a[i];	
			mx=max(mx,x);
		}
		printf("%d\n",mx);
	}
	return 0;
}