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 <map>

#define debug(x) cout << #x << "==" << x << endl;

using namespace std;

//??\???

int conv(string s) {
  string hh="", mm="", ss="";
  hh += s[0]; hh += s[1];
  mm += s[3]; mm += s[4];
  ss += s[6]; ss += s[7];

  return stoi(hh) * 60 * 60 + stoi(mm) * 60 + stoi(ss);
}

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

  int N;
  while(cin >> N) {

    if(N == 0) break;

    map<int,int> imos;
    for(int i = 0; i < N; i++) {
      string s1, s2;
      cin >> s1 >> s2;
      imos[ conv(s1) ] += 1;
      imos[ conv(s2) ] -= 1;
    }

    int mx = 0, num = 0;
    for(map<int,int>::iterator it = imos.begin(); it != imos.end(); it++) {
      num += (it -> second);
      mx = max(mx, num);
    }
    cout << mx << endl;
  }

  return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<map>
#include<algorithm>
using namespace std;
typedef pair<int,int> se;
typedef vector<se> tt;
int main(){
  int n;
  cin>> n;
  while(n!=0){
    int i,j,k;
    string str;
    tt t;
    for(i=0;i<n;i++){
      int st=0,et=0;
      cin >> str;
      st+=((str[0]-'0')*10+str[1]-'0')*24*60
	+((str[3]-'0')*10+str[4]-'0')*60+((str[6]-'0')*10+str[7]-'0');
      cin >> str;
      et+=((str[0]-'0')*10+str[1]-'0')*24*60
	+((str[3]-'0')*10+str[4]-'0')*60+((str[6]-'0')*10+str[7]-'0');
      t.push_back(make_pair(st,et));
    }
    sort(t.begin(),t.end());
    int m=0,b;
    for(j=0;j<86401;j++) {
      b=0;
      for(k=0;k<t.size();k++){
	if(t[k].first<=j&&j<t[k].second) b++;
      }
      if(m<b) m=b;
    }
    cout << m << endl;
    cin >> n;
  }
  return 0;
}

C++: //
//  main.cpp
//  Osaki
//
//  Created by x15071xx on 2017/06/22.
//  Copyright ?? 2017??´ AIT. All rights reserved.
//

#include <iostream>

using namespace std;
int main(int argc, const char * argv[]) {
    
    
    while (1) {
        int n,i,j,time[86400] = {0};
        cin >> n;
        
        if (n == 0) {
            break;
        }
        for (i = 0; i < n; i++) {
            
            int hs,ms,ss;
            int he,me,se;
            int ts,te;
            cin >> hs; cin.ignore(); cin >> ms; cin.ignore(); cin >> ss;
            cin >> he; cin.ignore(); cin >> me; cin.ignore(); cin >> se;
            
            ts = hs*3600 + ms*60 + ms;
            te = he*3600 + me*60 + me;
            
            for (j = ts; j < te; j++) {
                time[j]++;
            }
        }
        
        int max = 0;
        for (i = 0; i < 86401; i++) {
            if (max < time[i]) {
                max = time[i];
            }
        }
        
        cout << max << endl;
        
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef vector<int> V;
const long long MOD=1000000007LL;
const long long INFL=1LL << 60;
const int INF=1<<29;


int main() {
    while(1){
        int N; cin >>N;
        if(!N)
            break;
        int T=24*60*60;
        V time(T,0);
        for(int i=0;i<N;i++){
            string S,G;
            cin >>S>>G;
            int S_time,G_time;
            S_time=(S[0]-'0')*36000+(S[1]-'0')*3600
            +(S[3]-'0')*600+(S[4]-'0')*60+(S[6]-'0')*10
            +S[7]-'0';
            G_time=(G[0]-'0')*36000+(G[1]-'0')*3600
            +(G[3]-'0')*600+(G[4]-'0')*60+(G[6]-'0')*10
            +G[7]-'0';
            time.at(S_time)++;
            time.at(G_time)--;
        }
        for(int i=0;i<T;i++){
            if(0<i)time.at(i)+=time.at(i-1);
        }
        int M=0;
        for(int i=0;i<T;i++){
            if(M<time.at(i))M=time.at(i);
        }
        cout <<M<<endl;
    }
    return 0;
}

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

int main(){
  int i,j,n,h1[10000],m1[10000],s1[10000],h2[10000],m2[10000],s2[10000],c,ans;
  while(1){
    cin >> n;
    if(n == 0) break;
    for(i=0;i<n;i++){
      scanf("%d:%d:%d",&h1[i],&m1[i],&s1[i]);
      scanf("%d:%d:%d",&h2[i],&m2[i],&s2[i]);
    }

    ans = c = 1;
    for(i=0;i<n;i++){
      for(j=0;j<n;j++){
	if(i == j) continue;
	else if((h2[i] < h1[j]) || (h2[i] == h1[j] && m2[i] < m1[j]) || (h2[i] == h1[j] && m2[i] == m1[j] && s2[i] <= s1[j])) continue;
	else if((h2[j] < h1[i]) || (h2[j] == h1[i] && m2[j] < m1[i]) || (h2[j] == h1[i] && m2[j] == m1[i] && s2[j] <= s1[i])) continue;
	else{ c++;
	  //	  cout << "i=" << i << " j=" << j << " ";
	}
      }
      if(ans < c) ans = c;
      c = 1;
    }

    cout << ans << endl;

  }
  return 0;
}