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 <algorithm>
using namespace std;

const int TIME = 60 * 60 * 24 + 60;
int data[TIME];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	while(cin >> n && n){
		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 <iostream>
#include <string>
#include <vector>
using namespace std;

typedef long long ll;

ll f(string s){
    string s1,s2,s3;
    s1 = s.substr(0,2);
    s2 = s.substr(3,2);
    s3 = s.substr(6,2);

    int h = stoi(s1)*3600;
    int m = stoi(s2)*60;
    int ss = stoi(s3)*1;

    return h+m+ss;
}

void solve(int n){
    vector<int> v(60*60*60+3600+60+10,0);
    for(int i=0;i<n;i++){
        string s1,s2;
        cin >> s1 >> s2;
        ll s=f(s1);
        ll t=f(s2);
        v[s]++;
        v[t]--;
    }
    for(int i=1;i<60*60*60+60*60+60;i++){
        v[i] = v[i] + v[i-1];
    }
    int ans = -1;
    for(int i=1;i<60*60*60+60*60+60;i++){
        ans = max(ans,v[i]);
        if(v[i] == 6)  cout << i << endl;
    }
    cout << ans << endl;
}

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

C++: #include<bits/stdc++.h>
#define range(i,a,b) for(int i = (a); i < (b); i++)
#define rep(i,b) range(i,0,b)
#define pb(a) push_back(a)
#define all(a) (a).begin(), (a).end()
#define debug(x) cout << "debug " << x << endl;
using namespace std;

int main(){
    int n;
    while(cin >> n,n){
        int t[86500] = {0};
        rep(i,n){
            int h,m,s;
            char g;
            cin >> h >> g >> m >> g >> s;
            t[h * 3600 + m * 60 + s]+=1;
            cin >> h >> g >> m >> g >> s;
            t[h * 3600 + m * 60 + s]-=1;
        }
        int ans = 0, train = 0;
        rep(i,86500){
            train+=t[i];
            ans = max(ans, train);
        }
        cout << ans << endl;
    }
}

C++: #include <bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef vector<int>    VI;
typedef vector<bool>   VB;
typedef vector<string> VS;

#define MP make_pair
#define PB push_back
#define ALL(x)  (x).begin(),(x).end()
#define rep(i, N)  for (int i = 0; i < (int)(N); i++)
#define REP(i, init, N)  for (int i = (init); i < (int)(N); i++)
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl

int n;
VI ss, gs;

bool check(int s, VI& used, VI& gts) {
	rep (i, gts.size()) {
		if (s >= gts[i] && !used[i]) {
			used[i] = true;
			return true;
		}
	}
	return false;
}

int main(void) {
	while (1) {
		ss.clear();
		gs.clear();
		cin >> n;
		if (n == 0) break;
		rep (i, n) {
			int h, m, s;
			scanf("%d:%d:%d", &h, &m, &s);
			int stime = h * 60 * 60;
			stime += m * 60;
			stime += s;
			scanf("%d:%d:%d", &h, &m, &s);
			int gtime = h * 60 * 60;
			gtime += m * 60;
			gtime += s;
			ss.PB(stime);
			gs.PB(gtime);
		}
		VI used;
		VI gts;
		int ans = 0;
		rep (i, n) {
			if (!check(ss[i], used, gts)) {
				ans++;
			}
			used.PB(false);
			gts.PB(gs[i]);
		}
		cout << ans << endl;
	}
    return 0;
}

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

#define rep(i,n) for(int i=0;i<n;i++)
#define REP(n) rep(i,n)
#define all(n) n.begin(),n.end()

const int H = 10000, M = 100, CHAKU = 0, HATU = 1;

typedef pair<int, int> pp;

int main()
{
    int n;
    while(cin >> n && n)
    {
        int ans = 0, h, m, s;
        char t;
        vector<pp> tr;
        REP(n)
        {
            cin >> h >> t >> m >> t >> s;
            tr.push_back(pp(h * H + m * M + s, HATU));
            cin >> h >> t >> m >> t >> s;
            tr.push_back(pp(h * H + m * M + s, CHAKU));
        }
        sort(all(tr));

        int num = 0;
        REP(n)
            if(tr[i].second == CHAKU) num--;
            else { num++; ans = max(ans, num);}

        cout << ans << endl;
    }
    return 0;
}

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

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