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 <string>
#include <vector>
#include <algorithm>
#include <functional>
#include<numeric>
#include<cmath>
#include<stdio.h>
#define REP(i, n) for(int i = 0; i < n; i++)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOR(i, m, n) for(int i = m; i < n; i++)
#define INF 2e9
#define ALL(v) v.begin(), v.end()
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<ll,ll> pll;
const ll inf = 1LL << 60;
const int day = 24*3600;

int main(){
    //cin.tie(nullptr);
	//ios_base::sync_with_stdio(false);
	//cout << fixed << setprecision(15);
    vector<int> ans;
    while(true){
        int n; cin>>n;
        if(n == 0)break;
        else{
            vector<int> imos(day,0);
            vector<int> ruiseki(day,0);
            REP(i,n){
                int a,b,c,d,e,f;
                scanf("%d:%d:%d %d:%d:%d", &a,&b,&c,&d,&e,&f);
                (void)getchar();
                //cout << a << b <<c<<d<<e<<f<<endl;
                int start = 3600*a + 60*b + c;
                int end = 3600*d + 60*e + f;
                imos[start] += 1;
                imos[end] -= 1;
            }
            ruiseki[0] = imos[0];
            int maxi = 0;
            REP(i,day-1){
                ruiseki[i+1] = ruiseki[i] + imos[i+1];
                maxi = max(maxi,ruiseki[i+1]);
            }

            ans.push_back(maxi);

        }
    }

    REP(i,ans.size()){
        cout<<ans[i] <<endl;
    }
}

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

using namespace std;

const int seconds = 60;
const int minutes = 60;
const int hours = 24;
const int day = seconds*minutes*hours;

vector<string> split(string s, char delimeter){
    string t = "";
    vector<string> ret;
    for(int i=0; i<s.length(); i++){
        if(s[i] != delimeter){
            t += s[i];
        }else{
            ret.push_back(t);
            t = "";
        } 
    }
    if (t != "")ret.push_back(t);
    return ret;
}

int intTime(string stime){
    vector<string> time = split(stime, ':');

    int h = ((time[0][0]-'0')*10 + (time[0][1]-'0'))*minutes*seconds;
    int m = ((time[1][0]-'0')*10 + (time[1][1]-'0'))*seconds;
    int s = ((time[2][0]-'0')*10 + (time[2][1]-'0'));

    return h+m+s;
}

int main(){
    vector<int> ans;

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

        if(n == 0) break;

        int sum[day+1];
        fill(sum, sum+day, 0);

        string a, b;
        for(int i=0; i<n; i++){
            cin >> a >> b;
            sum[intTime(a)]++;
            sum[intTime(b)]--;
        }

        int ret = sum[0];
        for(int i=0; i<day-1; i++){
            sum[i+1] += sum[i];
            if(ret < sum[i+1]) ret = sum[i+1];
        }
        ans.push_back(ret);
    }

    for(int i=0; i<ans.size(); i++){
        cout << ans[i] << endl;
    }

    return 0;
}

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

const int TIME = 60 * 60 * 25 + 60 * 60 + 60;
int data[TIME];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	while(cin >> n && n != 0){
		for(int i = 0; i < TIME; ++i){
			data[i] = 0;
		}
		
		int a, b, c;
		for(int i = 0; i < n; ++i){
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] ++;
			
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] --;
		}
	
		int ans = 0;
		for(int i = 0; i < TIME; ++i){
			if(i > 0)
				data[i] += data[i - 1];
			ans = max(ans, data[i]);
		}
		
		cout << ans << endl;
	}
	return 0;
}

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


bool isso(long long int a) {
	if (a == 1 || a == 0)return false;
	for (long long int i = 2; i*i <= a; ++i) {
		if ((a%i)) {
		}
		else {
			return false;
		}
	}
	return true;
}
int main() {
	while (1) {
		int n; cin >> n;
		if (!n)break;
		int aa[100000];
		memset(aa, 0, sizeof(aa));
		for (int i = 0; i < n; ++i) {
			int t[2];
			for (int j = 0; j < 2; ++j) {
				int atime = 0;
				string st; cin >> st;
				atime += stoi(st.substr(0, 2)) * 3600;
				atime += stoi(st.substr(3, 2)) * 60;
				atime += stoi(st.substr(6, 2));
				t[j] = atime;
			}
			aa[t[0]] += 1;
			aa[t[1]] -= 1;
		}
		int now = 0;
		int amax = 0;
		for (int i = 0; i < 100000; ++i) {
			now += aa[i];
			amax = max(now, amax);
		}
		cout << amax << endl;
	}
	return 0;
}

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

struct TIME {
	int time;
	int start;
	bool operator<(const TIME &t){
		if( time == t.time ){
			return start<t.start;
		}
		return time<t.time;
	}
};

int main() {
	while(true){
		
		vector<TIME> times;
		
		int n;
		cin >> n;
		if(n==0)break;
		
		for(int i=0;i<n;i++){
			int h,m,s;
			char c;
			cin >> h >> c >> m >> c >> s;
//			cout << h <<":"<<m<<":"<<s <<endl; 
			TIME t0={h*60*60+m*60+s,1};
			times.push_back(t0);

			cin >> h >> c >> m >> c >> s;
//			cout << h <<":"<<m<<":"<<s<<endl; 
			TIME t1={h*60*60+m*60+s,0};
			times.push_back(t1);
		}

		sort( times.begin(),times.end());

		int count=0;
		int ans=0;
		for(TIME &t : times){
//			cout << t.start << " " << t.time << endl;;
			if(t.start==1){
				count++;
				ans=max(count,ans);
			}else{
				count--;
			}
		}
		cout << ans << endl;
	}
	
	
	return 0;
}