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 INF 2000000000
#define int long long int
#define MOD 1000000007
#define pb push_back
#define cin1(n) (cin >> n)
#define cin2(a,b) (cin >> a >> b)
#define cin3(a,b,c) (cin >> a >> b >> c)
#define cout(n) (cout << n << endl)
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define fr first 
#define sc second 
#define EPS (1e-10)

using namespace std;

typedef vector<int> vi;
typedef vector< vector<int> > vvi;
typedef vector<pair<int,int>> vpii;
typedef vector<string> vs;
typedef vector<vector<string>> vss;
typedef pair<int,int> pii;

int dx[] = {1,-1,0,0};
int dy[] = {0,0,1,-1};
int n,m;
int a,b;
int p,q;

pii input(string t1,string t2) {
	int ret1,ret2;

	ret1 = stoi(t1.substr(6,2)) + 60 * stoi(t1.substr(3,2)) + 60 * 60 * stoi(t1.substr(0,2));
	ret2 = stoi(t2.substr(6,2)) + 60 * stoi(t2.substr(3,2)) + 60 * 60 * stoi(t2.substr(0,2));
	return make_pair(ret1,ret2);
}

signed main() {

	while(1) {
		cin1(n);
		if (n == 0) break;

		vpii table(n,make_pair(0,0));
		rep(i,0,n) {
			string time1,time2;
			cin2(time1,time2);
			table[i] = input(time1,time2);	
			//cout << table[i].fr << " " << table[i].sc << endl;
		}
		
		int idx = 0;
		vector<pair<bool,int>> train;
		train.pb(make_pair(true,0));
		rep(i,0,60*60*24) {
			//std::cout << "table.fr " << table[idx].fr <<  std::endl;
			rep(j,0,train.size()) {
				if (train[j].sc == i) {
					train[j].fr = true;
				}
			}
			if (table[idx].fr == i) {
				//cout("in if");
				//cout(table[idx].fr);
				bool flag = false;
				rep(j,0,train.size()) {
					if (train[j].fr) {
						train[j].fr = false;
						train[j].sc = table[idx].sc;
						flag = true;
						break;
					}
				}
				if (!flag) {
					train.pb(make_pair(false,table[idx].sc));
				}
				idx++;
			}
		}
		cout(train.size());
	}

	return 0;
}

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

int main(void){

  int n;
  int sum[3000];

  while(1){
        scanf("%d",&n);
        if(n==0)break;
        memset(sum,0,sizeof(sum));
        for(int i=0;i<n;i++){
            int h,m,s;
            scanf("%2d:%2d:%2d",&h,&m,&s);
            sum[h*60*60+m*60+s]++;
            scanf("%2d:%2d:%2d",&h,&m,&s);
            sum[h*60*60+m*60+s]--;
        }
        int res=sum[0];
        for(int i=0;i<=24*60*60;i++){
            sum[i+1]+=sum[i];
            res=max(res,sum[i+1]);
        }
        printf("%d\n",res);
    }
    return 0;
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <cstring>
#include <vector>
#include <algorithm>
#include <tuple>
#include <queue>
#include <set>
#include <cstdio>
#include <climits>
#include <cmath>
#include <array>
#include <functional>
#include <sstream>
#include <list>
#include <set>
const int MOD=1000000007;
const int INF=1000000000;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
const double eps=1e-9;
const int inf=1e9;
typedef pair<int,int> P;
struct Point
{
  double x,y;
  Point(){x=0;y=0;}
  Point(double d_x,double d_y){x=d_x,y=d_y;}
  double operator*(Point obj){return obj.x*x+obj.y*y;}
  double operator%(Point obj){return obj.y*x-obj.x*y;}
  Point operator*(double b){Point tmp;tmp.x=x*b;tmp.y=y*b;return tmp;}
  Point operator/(double b){Point tmp;tmp.x=x/b;tmp.y=y/b;return tmp;}
  Point operator+(Point obj){Point tmp;tmp.x=x+obj.x;tmp.y=y+obj.y;return tmp;}
  Point operator-(){Point tmp;tmp.x=-x;tmp.y=-y;return tmp;}
  Point operator-(Point obj){Point tmp;tmp.x=x-obj.x;tmp.y=y-obj.y;return tmp;}
  Point operator-=(Point obj){x-=obj.x;y-=obj.y;return *this;}
  Point operator+=(Point obj){x+=obj.x;y+=obj.y;return *this;}
  Point operator/=(double b){x=x/b;y=y/b;return *this;}
  Point operator*=(double b){x=x*b;y=y*b;return *this;}
  double size(){return hypot(x,y);}
  Point unit(){return Point(x/size(),y/size());}
  Point normal(){return Point(y,-x);}
  double atan(){return atan2(y,x);}
};

bool operator<(Point a,Point b){return a.x!=b.x?a.x<b.x:a.y<b.y;}
bool operator>(Point a,Point b){return b<a;}
bool operator<=(Point a,Point b){return !(b<a);}
bool operator>=(Point a,Point b){return !(a<b);}
bool operator==(Point a,Point b){return (a-b).size()<eps;}
bool operator!=(Point a,Point b){return !(a==b);}

bool equal(double a,double b){return abs(a-b)<eps;}
double cross(Point a,Point b){return a%b;}
double dot(Point a,Point b){return a*b;}

int ccw(Point a,Point b,Point c)
{
  b=b-a;
  c=c-a;
  if(b%c>0) return +1;
  else if(b%c<0)return -1;
  else if(b*c<0) return +2;
  else if(b.size()<c.size()) return -2;
  else return 0;
}


int times[100005];
int n;

void calc(string str,int v)
{
  stringstream ss(str);
  int h,m,s;
  char c;
  ss >> h >> c >> m >> c >> s;
  times[h*60*60+m*60+s]+=v;
}


int main(int argc,char const* argv[])
{
  while(1)
    {
      memset(times,0,sizeof(times));
      cin >> n;
      if(!n)break;
      for(int i=0;i<n;i++)
	{
	  string start,goal;
	  cin >> start >> goal;
	  calc(start,1);
	  calc(goal,-1);
	}
      for(int i=1;i<100000;i++)
	{
	  times[i]+=times[i-1];
	}
      int ans=0;
      for(int i=0;i<100000;i++)
	{
	  ans=max(ans,times[i]); 
	}
      cout << ans << endl;
    }
  return 0;
}