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 <cstdio>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;

typedef pair< int, int > iP;

int main() {

    int n;

    while(cin >> n, n) {
        vector< iP > v;
        vector< int > t(24 * 3600, 0);
        for(int i = 0; i < n; i++) {
            int h, m, s, hh, mm, ss;
            scanf("%2d:%2d:%2d %2d:%2d:%2d", &h, &m, &s, &hh, &mm, &ss);
            v.push_back(iP(h * 3600 + m * 60 + s, hh * 3600 + mm * 60 + ss));
            t[v[v.size() - 1].first]++, t[v[v.size() - 1].second]--;
        }

        for(int i = 1; i < 24 * 3600; i++) {
            t[i] += t[i - 1];
        }
        cout << *max_element(t.begin(), t.end()) << endl;
    }
}

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

#define rep(i, n)       rep2 (i, 0, n)
#define rep2(i, m, n)   for  (int i = (int)(m); i < (int)(n); ++i)

typedef pair<int, int> pi;

int main()
{
    int n, h, m, s;
    while (scanf("%d", &n), n) {
        vector<pi> v;
        rep (i, n) {
            scanf("%d:%d:%d", &h, &m, &s);
            v.push_back((pi){ h * 3600 + m * 60 + s, 1 });
            scanf("%d:%d:%d", &h, &m, &s);
            v.push_back((pi){ h * 3600 + m * 60 + s, -1 });
        }
        sort(v.begin(), v.end());
        
        int ans = 0, cur = 0;
        rep (i, v.size()) {
            cur += v[i].second;
            ans = max(ans, cur);
        }
        
        printf("%d\n", ans);
    }
}

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;
    int m = 0;
    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 = m + 1; j < n; j++){
        if(time[j].first == i){
          m++;
          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>
using namespace std;

int main(){
    int n;
    while(cin>>n){
        if(n==0) break;
        int k=24*60*60;
        int imos[k+1]={};
        for(int i=0;i<n;i++){
            string l;
            cin>>l;
            int a=((l[0]-'0')*10 + (l[1]-'0'))*60*60 + ((l[3]-'0')*10 + (l[4]-'0'))*60 + ((l[6]-'0')*10 + (l[7]-'0'));
            imos[a]++;
            //cerr<<a<<endl;
            cin>>l;
            a=((l[0]-'0')*10 + (l[1]-'0'))*60*60 + ((l[3]-'0')*10 + (l[4]-'0'))*60 + ((l[6]-'0')*10 + (l[7]-'0'));
            imos[a]--;
            //cerr<<a<<endl;
        }
        for(int i=0;i<k;i++){
            imos[i+1]+=imos[i];
        }
        int ans=0;
        for(int i=0;i<k;i++){
            ans=max(ans,imos[i]);
            
        }
        cout<<ans<<endl;
    }
    
}

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;
}