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 <algorithm>
#include <vector>
#include <functional>
#include <queue>
#include <string>
#include <cstring>
#include <numeric>
#include <cstdlib>
#include <cmath>
#include <map>
#include <unordered_map>
#include <set>
using namespace std;

typedef long long ll;

#define INF 10e17
#define rep(i,n) for(int i=0; i<n; i++)
#define rep_r(i,n,m) for(int i=m; i<n; i++)
#define END cout << endl
#define MOD 1000000007
#define pb push_back
#define sorti(x) sort(x.begin(), x.end())
#define sortd(x) sort(x.begin(), x.end(), std::greater<int>())
#define debug(x) std::cerr << (x) << std::endl;
#define roll(x) for (auto itr : x) { debug(itr); }

template <class T> inline void chmax(T &ans, T t) { if (t > ans) ans = t;}
template <class T> inline void chmin(T &ans, T t) { if (t < ans) ans = t;}

using ps = pair<string, string>;

constexpr int MINI = 60;
constexpr int SEC = 60;
constexpr int HOUR = 24;

int timeToInt (string time) {
  int t1 = stoi(time.substr(0,2));
  int t2 = stoi(time.substr(3,5));
  int t3 = stoi(time.substr(6));
  return t1 * 3600 + t2 * 60 + t3;
}

int overlap_trains(int n, vector<ps> const& trains) {
  int ans = 0;
  vector<int> overlap(MINI * SEC * HOUR + 1000, 0);
  for (int i = 0; i < n; ++i) {
    int begin = timeToInt(trains[i].first); 
    int end = timeToInt(trains[i].second);

    rep_r(i, end, begin) overlap[i] += 1;
  }

  for (auto itr : overlap) chmax(ans, itr);
  return ans;
}

int main() {
  int n;
  while (cin >> n and n != 0) {
    string s1, s2;
    vector<ps> trains(n);
    rep(i, n) {
      cin >> s1 >> s2;
      trains[i] = ps(s1, s2);
    }
    cout << overlap_trains(n, trains) << endl;
  }
}

C++: #include <bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<map>
#include<cstring>
#include<string>
#include <math.h>
#include<algorithm>
#include<functional>
#define int long long
#define ll long long
#define inf  1000000007
#define mod 1000000007
#define pa pair<int,int>
#define pal pair<ll,ll>
#define ppa pair<int,pa>
#define EPS (1e-10)
#define equals(a,b) (fabs((a)-(b))<EPS)

using namespace std;

class Point{
  public:
  double x,y;
  Point(double x=0,double y=0):x(x),y(y) {}
  Point operator + (Point p) {return Point(x+p.x,y+p.y);}
  Point operator - (Point p) {return Point(x-p.x,y-p.y);}
  Point operator * (double a) {return Point(x*a,y*a);}
  Point operator / (double a) {return Point(x/a,y/a);}
  double absv() {return sqrt(norm());}
  double norm() {return x*x+y*y;}
  bool operator < (const Point &p) const{
    return x != p.x ? x<p.x: y<p.y;
  }
  bool operator == (const Point &p) const{
    return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
  }
};
typedef Point Vector;

struct Segment{
Point p1,p2;
};

double hen(Vector a){
if(fabs(a.x)<EPS && a.y>0) return acos(0);
else if(fabs(a.x)<EPS && a.y<0) return 3*acos(0);
else if(fabs(a.y)<EPS && a.x<0) return 2*acos(0);
else if(fabs(a.y)<EPS && a.x>0) return 0.0;
else if(a.y>0) return acos(a.x/a.absv());
else return 2*acos(0)+acos(-a.x/a.absv());

}

double dot(Vector a,Vector b){
  return a.x*b.x+a.y*b.y;
}
double cross(Vector a,Vector b){
  return a.x*b.y-a.y*b.x;
}
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int ru[11]={1,2,4,8,16,32,64,128,256,512,1024};

ll frac[100010];
ll inv[100010];

ll saikif(ll a,int n){
  if(n==1) return a%mod;
  else if(n%2==0){
    ll q=saikif(a,n/2);
    return (q*q)%mod;
  }
  else return (a*saikif(a,n-1))%mod;
}

void gyakugen(){
  frac[0]=1;
  for(int i=1;i<=100000;i++) frac[i]=(frac[i-1]*i)%mod;
  for(int i=0;i<=100000;i++) inv[i]=saikif(frac[i],mod-2);
}


//----------------kokomade temple------------


signed main(){
string s,t;
int n;
int k=0;
while(cin>>n){

  if(n==0) break;
pa a[10010];
for(int i=0;i<n;i++){
 cin>>s>>t;
int a1=0,a2=0;
a1 += (s[0]-'0')*36000+(s[1]-'0')*3600+(s[3]-'0')*600+(s[4]-'0')*60+(s[6]-'0')*10+(s[7]-'0');
 a2 += (t[0]-'0')*36000+(t[1]-'0')*3600+(t[3]-'0')*600+(t[4]-'0')*60+(t[6]-'0')*10+(t[7]-'0');
a[i].first=a1;
a[i].second=a2;
//cout<<a1<<" "<<a2<<endl;
}
int z[100000]={0};
for(int i=0;i<n;i++){
  z[a[i].first]++;
  z[a[i].second]--;
}
for(int i=1;i<90000;i++){
  z[i] += z[i-1];
}

int ma=0;
for(int i=0;i<90000;i++){
  ma=max(ma,z[i]);
}

cout<<ma<<endl;
}

return 0;
}