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<fstream>
#include<sstream>
#include<vector>
#include<algorithm>
#include<string>
#include<cstring>
#include<cmath>
#include<iomanip>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<list>
#include<utility>
#include<climits>

#define INF INT_MAX/2
#define EPS 1.0e-7

using namespace std;

typedef long long ll;
typedef pair<int,int> PII;
typedef pair<int,PII> PIII;

int N;

vector<PII> compress(vector<PIII> &v, vector<PIII> &s, vector<PIII> &e){

    vector<PIII> cv(v.size());

    for(unsigned int i=0;i<v.size();++i)cv[i] = v[i];
    sort(cv.begin(),cv.end());
    int n = unique(cv.begin(),cv.end()) - cv.begin();

    vector<PII> ret(v.size()/2);
    for(unsigned int i=0;i<v.size()/2;++i){
        int si = lower_bound(cv.begin(),cv.begin()+n,s[i]) - cv.begin();
        int ei = lower_bound(cv.begin(),cv.begin()+n,e[i]) - cv.begin();
        ret[i] = make_pair(si,ei);
    }

    return ret;

}

int main(){

    cin.sync_with_stdio(false);

    while(cin >> N,N){

        vector<PIII> v(2*N);
        vector<PIII> s(N);
        vector<PIII> e(N);

        for(int i=0;i<N;++i){

            int h,m,sec;
            string st,et;

            cin >> st >> et;

            sscanf(st.c_str(),"%d:%d:%d",&h,&m,&sec);
            v[2*i] = make_pair(h,make_pair(m,sec));
            s[i] = v[2*i];

            sscanf(et.c_str(),"%d:%d:%d",&h,&m,&sec);
            v[2*i+1] = make_pair(h,make_pair(m,sec));
            e[i] = v[2*i+1];

        }

        vector<PII> p = compress(v,s,e);

        vector<int> cnt(2*N);

        for(int i=0;i<N;++i){
            cnt[p[i].first]++;
            cnt[p[i].second]--;
        }

        for(int i=1;i<2*N;++i)
            cnt[i] += cnt[i-1];

        int ans=0;

        for(int i=0;i<2*N;++i)
            ans = max(ans,cnt[i]);

        cout << ans << endl;

    }

    return 0;

}

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

//define
#define ALL(a) a.begin(),a.end()
#define REP(i,n) for(int i=0;i<n;i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)
#define debug(x) if(1) cout<<#x<<":"<<x<<endl;
#define DEBUG(x) if(1) cout<<#x<<":"<<x<<endl;
#define ll long long

//constant
const int MOD=1000000007;
const int INF=INT_MAX/3-1;
const double EPS=1e-9;
const int dx[]={1,0,-1,0};
const int dy[]={0,1,0,-1};

//typedef
typedef vector<int> vi;
typedef vector<vector<int>> vvi;






int main(){
    int n;
    while(cin>>n,n){
        vector<pair<int,bool>> timer;
        string buf;
        REP(i,n){
            REP(j,2){
            cin>>buf;
            int hh=stoi(buf.substr(0,2));
            int mm=stoi(buf.substr(3,2));
            int ss=stoi(buf.substr(6,2));
            timer.push_back(make_pair(ss+mm*60+hh*60*60,j));
            }

        }
        sort(ALL(timer),[](pair<int,bool> lef,pair<int,bool> rig)
        {return lef.first<rig.first ||
                lef.first==rig.first && !lef.second;});
        int running=0;
        int stop=0;
        REP(i,n*2){
            if(!timer[i].second){
                if(stop)
                    stop--;
                else
                    running++;


            }
 else if(timer[i].second){
                stop++;


            }



        }
            cout<<running<<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 };

static const int MAX = 24 * 3600 + 60*60 + 60;
int t[MAX];

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

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

		rep(i,0,MAX) 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,MAX) {
			tmp += t[i];
			ans = max(ans, tmp);
		}
		cout << ans << endl;
	}

	return 0;
}

C++: #include<iostream>
#include<list>
#include<vector>
#include<algorithm>
#include<string>
#include<stdio.h>
#include<math.h>
#include<unordered_map>

using namespace std;
using vec = vector<int>;
using mat = vector<vec>;
using lst = list<int>;


class Event
{
public:
	int add;
	string time;

	Event(int a)
	{
		add = a;
		cin >> time;
	}

	bool operator<(const Event & a)const
	{
		return time < a.time;
	}
};


bool solve()
{
	int n; cin >> n;
	if (n == 0)return false;

	list<Event> eLst;

	for (int i = 0; i < n; ++i)
	{
		eLst.emplace_back(1);
		eLst.emplace_back(-1);
	}
	eLst.sort();

	int ans = 0, num = 0;
	while (!eLst.empty())
	{
		num += eLst.front().add;
		ans = max(ans, num);
		eLst.pop_front();
	}

	cout << ans << endl;

	return true;
}


int main()
{
	while (solve());

	return 0;
}