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"
#define rep(i,n) for(int i = 0; i < (n); ++i)
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const int MAX_TIME = 24*60*60 + 1;

int calcTime(string s){
    int ret = (s[0] - '0') * 60 * 60 * 10;
    ret += (s[1] - '0') * 60 * 60;
    ret += (s[3] - '0') * 60 * 10;
    ret += (s[4] - '0') * 60;
    ret += (s[6] - '0') * 10;
    ret += (s[7] - '0');
    return ret;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
    while(true){
        int n;
        cin >> n;
        if(n == 0) break;
        vector<int> ims(MAX_TIME, 0);
        rep(i,n){
            string s;
            cin >> s;
            ims[calcTime(s)]++;
            cin >> s;
            ims[calcTime(s)]--;
        }
        int ans = 0;
        rep(i,MAX_TIME-1){
            ims[i+1] += ims[i];
            chmax(ans, ims[i]);
        }
        cout << ans << endl;
    }
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define min(a,b) ((a)<(b)?(a):(b))
#define max(a,b) ((a)>(b)?(a):(b))
#define REP(i,n) for(int i=0;i<n;i++)
#define FOR(i,n1,n2) for(int i=n1;i<n2;i++)
#define bFOR(i,n1,n2) for(int i=n1;i>=n2;i--)
#define speed_up    ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);

typedef long long int ll;
typedef pair<ll,ll> Pi;
const int INF=(ll)(1LL<<30)-1;
const double INFd=100000000000.0;
const ll INFl=(ll)9223372036854775807;
const int MAX=10000;
const ll MOD=(ll)1e9+7;
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a, b)*b;}
int dx[4]={0,1,0,-1},dy[4]={-1,0,1,0};

template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}

int n;
int main(){
	while(1){
		int ti[86410];
		REP(i,86410)ti[i]=0;
		cin>>n;
		if(n==0)break;
		REP(i,n){
			string s;
			cin>>s;
			int t=0;
			t+=36000*(s[0]-'0');
			t+=3600*(s[1]-'0');
			t+=600*(s[3]-'0');
			t+=60*(s[4]-'0');
			t+=10*(s[6]-'0');
			t+=(s[7]-'0');
			ti[t]+=1;
			cin>>s;
			t=0;
			t+=36000*(s[0]-'0');
			t+=3600*(s[1]-'0');
			t+=600*(s[3]-'0');
			t+=60*(s[4]-'0');
			t+=10*(s[6]-'0');
			t+=(s[7]-'0');
			ti[t]-=1;
		}
		for(int i=1;i<86410;i++){
			ti[i]=ti[i]+ti[i-1];
		}
		int ans=0;
		REP(i,86410){
			ans=max(ans,ti[i]);
		}
		cout<<ans<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)

void slove(int n){
	vector<int> v(86410);
	rep(i, 86410) v[i] = 0;//?????????
	rep(i, n){
		string s, e;
		cin >> s >> e;
		//?§???°?????????
		int start = 36000 * (s[0] - '0') + 3600 * (s[1] - '0') 
					+ 600 * (s[3] - '0') + 60 * (s[4] - '0')
					+ 10 * (s[6] - '0') + 1 * (s[7] - '0');
		int end = 36000 * (e[0] - '0') + 3600 * (e[1] - '0') 
					+ 600 * (e[3] - '0') + 60 * (e[4] - '0')
					+ 10 * (e[6] - '0') + 1 * (e[7] - '0');
		printf("%d %d\n", start, end);
		for (int j = start; j < end ; ++j) v[j]++;//???????????????
	}
	sort(all(v));
	reverse(all(v));
	printf("%d\n", v[0]);
}
int main(void){
	rep(i, 1000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

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

signed main() {
	int a;
	while (cin >> a,a) {
		multimap<int, int>s;
		multimap<int, int>o;
		for (int b = 0; b < a; b++) {
			string c;
			cin >> c;
			int e =(c[0]-48) * 36000 + (c[1] - 48) * 3600 + (c[3] - 48) * 600 + (c[4] - 48) * 60 + (c[6] - 48)*10+ (c[7] - 48);
			s.insert(pair<int, int>(e, 1));
			cin >> c;
			e = (c[0] - 48) * 36000 + (c[1] - 48) * 3600 + (c[3] - 48) * 600 + (c[4] - 48) * 60 + (c[6] - 48)*10 + (c[7] - 48);
			o.insert(pair<int, int>(e, -1));
		}
		for (auto w = s.begin(); w != s.end(); w++) {
			o.insert(pair<int, int>((*w).first, (*w).second));
		}
		int p = 0, q = 0;
		for (auto g = o.begin(); g != o.end(); g++) {
			q += (*g).second;
			p = max(p, q);
		}
		cout << p << endl;
	}
}

C++: #include "iostream"
#include "random"
#include "ctime"
#include "chrono"
#include "string"
#include "bitset"
#include "algorithm"
#include "map"

using namespace std;


int main() {
	int N;
	cin >> N;
	while (N) {
		vector<pair<string, string>>v(N);
		for (int i = 0; i < N; i++) {
			cin >> v[i].first >> v[i].second;
		}
		map<string, int>m;
		sort(v.begin(), v.end());
		int ans = 0;
		for (auto i : v) {
			if (m.empty()) {
				m[i.second]++;
				ans++;
				continue;
			}
			if ((*m.begin()).first <= i.first) {
				m[(*m.begin()).first]--;
				if ((*m.begin()).second == 0) {
					m.erase(m.begin());
				}
				m[i.second]++;
			}
			else {
				m[i.second]++;
				ans++;
			}
		}
		cout << ans << endl;
		cin >> N;
	}
	return 0;
}