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++)
#define ALL(a) (a).begin(),(a).end()
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define ll long long
#define ull unsigned long long
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
 
using namespace std;
const int TIME = 24*60*60;
int train_t[TIME+1]; 

int timeset(string s,int mode){
  int h = (s[0] - '0') * 10 + s[1] - '0';
  int m = (s[3] - '0') * 10 + s[4] - '0';
  int ss = (s[6] - '0') * 10 + s[7] - '0';
  int t = h * 60 * 60 + m * 60 + ss;
  if(mode)train_t[t] += 1;
  else train_t[t] -= 1;
}

int main(){
  int n;
  while(cin >> n){
    if(!n)break;
    REP(i,TIME)train_t[i] = 0;
    string s;
    REP(i,n){
      cin >> s;
      timeset(s,1);
      cin >> s;
      timeset(s,0);
    }
    int max_vehicle = 0;
    REP(i,TIME){
      train_t[i+1]+= train_t[i];
      max_vehicle = max(max_vehicle,train_t[i+1]);
    }
    cout << max_vehicle << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>
#include<cmath>
#include<cstring>
#include<queue>
#include<map>
#include<cstdio>
#include<climits>

#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 FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
using namespace std;
typedef pair<int, int> P;
typedef long long int ll;
typedef pair<ll,ll> LLP;
#define INF 1000000007
#define MOD 1000000007

#define ARRAY_MAX 100005

int d[ARRAY_MAX];

int main(){

    int n;
    while(cin >> n,n){
        REP(i,ARRAY_MAX){
            d[i] = 0;
        }
        int h,m,s;
        REP(i,n){
            scanf("%d:%d:%d",&h,&m,&s);
            d[3600*h+60*m+s]++;
            scanf("%d:%d:%d",&h,&m,&s);
            d[3600*h+60*m+s]--;
        }
        REP(i,ARRAY_MAX-1){
            d[i+1] += d[i];
        }
        int ans = 0;
        REP(i,ARRAY_MAX){
            ans = max(ans,d[i]);
        }
        cout << ans << endl;
    }


    return 0;
}

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

using namespace std;

int main(){
  int n;
  string st, ed;
  list<string> li;

  while(true){
    cin>>n;
    if(n==0) break;
    for(int i=0; i<n; ++i){
      cin>>st>>ed;
      if(li.size()==0){
	li.emplace_back(ed);
      }else{
	for(auto itr=li.begin(); itr!=li.end(); ){
	  if(*itr<=st){
	    li.erase(itr);
	    break;
	  }else{
	    ++itr;
	  }
	}
	li.emplace_back(ed);
      }
    }

    cout<<li.size()<<endl;
    li.clear();
    
  }


  return 0;
}

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

const int TIME = 60 * 60 * 100 + 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<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int toI(char c)
{
	return c - '0';
}
int main()
{
	int n;
	while (cin >> n && n != 0)
	{
		vector<pair<int, int> >range;
		vector<vector<pair<int, int> > > ansR;
		int ans = 1;
		for (int i = 0; i < n; i++)
		{
			pair<int, int> p;
			char line[15];
			cin >> line;
			int hour = toI(line[0]) * 10 + toI(line[1]);
			int minute = toI(line[3]) * 10 + toI(line[4]);
			int second = toI(line[6]) * 10 + toI(line[7]);
			p.first = hour * 60 * 60 + minute * 60 + second;
			cin >> line;
			hour = toI(line[0]) * 10 + toI(line[1]);
			minute = toI(line[3]) * 10 + toI(line[4]);
			second = toI(line[6]) * 10 + toI(line[7]);

			p.second = hour * 60 * 60 + minute * 60 + second;
			range.push_back(p);
		}
		sort(range.begin(), range.end());

		for (int i = 0; i < n; i++)
		{
			bool flag = false;
			for (int j = 0; j < ansR.size(); j++)
			{
				for (int k = 0; k < ansR.at(j).size(); k++)
				{
					if (range.at(i).first >= ansR.at(j).at(k).second ||
						range.at(i).second <= ansR.at(j).at(k).first)
					{
						ansR.at(j).push_back(range.at(i));
						flag = true;
						break;
					}
				}

				if (flag)break;
			}

			if (!flag)
			{
				vector<pair<int, int> > v;
				v.push_back(range[i]);
				ansR.push_back(v);
			}
		}

		cout << ansR.size() << endl;
	}
	return 0;
}