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 <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <string>
#include <stack>
#include <queue>
#include <cmath>
#include <cstdio>
#include <istream>
#include <sstream>
#include <iomanip>
using namespace std;

typedef ostringstream oss;
typedef istringstream iss;

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

typedef long L;
typedef long long LL;

const int DAY_OF_SECOND = 24 * 60 * 60;

// 複数文字split
vector<string> split(const string &str, const string &delim = " ") {
	int start = 0, pos;
	vector<string> result;
	
	while ( (pos = str.find_first_of( delim, start) ) != string::npos ) {
		if (pos - start != 0)
			result.push_back( str.substr( start, pos - start) );
		start = pos + 1;
	}

	return result;
}

LL toSecond(int h, int m, int s) {
	return (LL)h * 24 * 60 + (LL)m * 60 + s;
}

int main(void) {
	int N;
	while (cin >> N, N) {
		vi time(DAY_OF_SECOND, 0);

		for (int i = 0; i < N; i++) {
			int h, m, s;
			char buf;
			cin >> h >> buf >> m >> buf >> s;
			LL start = toSecond(h, m, s);
			cin >> h >> buf >> m >> buf >> s;
			LL end = toSecond(h, m, s);

			for (LL i = start; i < end; i++) {
				time[i]++;
			}
		}

		cout << *(max_element(time.begin(), time.end())) << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <cstdio>
using namespace std;
#define rep(i,a) for(int i = 0 ; i < a ; i ++)
int main(void){
  vector<int> ary(24*60*60,0);
  int n;
  while(cin>>n,n){
    char b[9],e[9];
    while(n--){
      cin>>b>>e;
      int h,m,s;
      sscanf(b,"%d:%d:%d",&h,&m,&s);
      int start = ((h * 60) + m) * 60 + s; 
      sscanf(e,"%d:%d:%d",&h,&m,&s);
      int finish = ((h * 60) + m) * 60 + s; 
      for(int i = start + 1 ; i < finish ; i ++)ary[i]++;
    }
    int ret = -1;
    for(int i = 0 ; i < ary.size() ; i ++)ret = max(ret,ary[i]);
    cout<<ret<<endl;
  }
}

C++: #include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdio>

using namespace std;

int main(){
  while(1){
  int n;
  cin >> n;
  if(n==0)break;

  int hs,ms,ss,he,me,se,S[10000],E[10000];

   for(int i=0; i < n; i++){
     scanf("%d:%d:%d",&hs,&ms,&ss);
     scanf("%d:%d:%d",&he,&me,&se);  
     S[i]=hs*10000+ms*100+ss;
     E[i]=he*10000+me*100+se;
   }
   int cnt=0,Max=0;
   for(int i=0; i < n-1 ;i++){
   for(int j=i+1; j < n ;j++){

     if(E[i] > S[j])cnt++;
     else break;
   }
   Max = max(Max,cnt);
   cnt = 0;
   }
   cout << Max+1 << endl;
   }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <utility>
#define REP(i,n) for(int i=0;i<(n);i++)
using namespace std;

int main()
{
  while(1){
    int n;
    scanf("%d", &n);
    if(n == 0) break;
    int ans = 1;
    pair<bool,int> train[n];
    REP(i,n)
      train[i].second = -1;
    train[0].first = false;
    pair<int,int> time[n];
    REP(i,n){
      int h, m, s;
      scanf("%d:%d:%d", &h, &m, &s);
      time[i].first = h*3600 + m*60 + s;
      scanf("%d:%d:%d", &h, &m, &s);
      time[i].second = h*3600 + m*60 + s;
    }
    train[0].second = time[0].second;
    REP(i,time[n-1].first+1){
      REP(j,ans)
        if(train[j].second == i){
          train[j].first = true;
          train[j].second = -1;
        }
      for(int j = 1; j < n; j++){
        if(time[j].first == i){
          bool flag = false;
          REP(k,ans){
            if(train[k].first){
              flag = true;
              train[k].first = false;
              train[k].second = time[j].second;
              break;
            }
          }
          if(!flag){
            train[ans].first = false;
            train[ans].second = time[j].second;
            ans++;
          }
        }
      }
    }
    cout << ans << endl;
  }
}

C++: #include <bits/stdc++.h>
typedef long long ll;
using namespace std;
#define repr(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define invrepr(i,a,b) for(int i=b-1;i>=a;i--)
#define invrep(i,n) invrepr(i,0,n)
#define repitr(itr,a) for(auto itr=a.begin();itr!=a.end();++itr)
#define P pair<int,int>
const int MOD=1e9+7;
const int INF=2e9;

int stoti(string s) {
    int res=0;
    rep(i,s.size()) {
        if (s[i]==':') continue;
        else {
            res*=10;
            res+=s[i]-'0';
        }
    }
    return res;
}

int main() {
    ios_base::sync_with_stdio(false);

    while (1) {
        int n;
        cin >> n;
        if (n==0) break;
        vector<P> p;
        rep(i,n) {
            string s,t;
            cin >> s >> t;
            p.push_back(make_pair(stoti(s),1));
            p.push_back(make_pair(stoti(t),-1));
        }
        sort(p.begin(),p.end());
        vector<int> a(2*n+1);
        int ans=0;
        rep(i,2*n) {
            a[i+1]=p[i].second;
            a[i+1]+=a[i];
            ans=max(ans,a[i+1]);
        }
        cout << ans << endl;
    }

    return 0;   
}