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<complex>
#include<iostream>
#include<iomanip>
#include<cmath>
#include<vector>
#include<map>
#include<ctime>
#include<sstream>
#include<cstdio>
#include<cstdlib>
#include<cassert>
#include<deque>
#include<queue>
#include<climits>
#include<list>
#include<stack>
#include<ctime>
#define all(n) n.begin(),n.end()
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define insert(a,b,c,d) PP(P(a,b),P(c,d))
#define F first
#define S second
#define pb push_back
#define INF (1<<27)
#define EPS 1e-10
#define equals(a,b) (fabs((a)-(b)) < EPS)
#define MAX_N 1000000
using namespace std;
typedef pair<int,int> P;
typedef pair<P,P> PP;
typedef unsigned long long ull;
typedef long long ll;
const int dx[4] = {0,1,0,-1};
const int dy[4] = {1,0,-1,0};

int get_time(string s){
  for(int i=0;i<s.length();i++)if(s[i] == ':')s[i] = ' ';
  stringstream ss;
  ss << s;
  int three[3];
  ss >> three[0] >> three[1] >> three[2];
 
  int sum = 0;
  sum += three[0]*60*60 + three[1]*60 + three[2];
  return sum;
}

bool cmp(const P &p,const P &q){
  if(p.F != q.F)return p.F > q.F;
  return p.F > q.S;
}

template <class T>
class RMQ_segment{
private:
  int n;
  T dat[2*MAX_N-1];
public:
  void init(int n_){
    n = 1;
    while(n<n_)n*=2;
    for(int i=0;i<2*n-1;i++)dat[i] = 0;
  }

  void update(int k,T a){
    k += n-1;
    dat[k] = a;
    while(k > 0){
      k = (k-1)/2;
      dat[k] = max(dat[k*2+1],dat[k*2+2]);
    }
  }

  T _query(int a,int b,int k,int l,int r){
    if(r<=a || b<=l)return 0;
    else if(a<=l && r<=b)return dat[k];

    T vl = _query(a,b,k*2+1,l,(l+r)/2);
    T vr = _query(a,b,k*2+2,(l+r)/2,r);
    return max(vl,vr);
  }

  T query(int a,int b){
    return _query(a,b,0,0,n);
  }


};


int main(){
  int n;
  //clock_t start,end;
  //start = clock(); 
  while(cin >> n && n){  
    vector<P> vec;
    rep(i,n){
      string st,ed;
      cin >> st >> ed;
      vec.pb(P(get_time(st),get_time(ed)));
    }
    RMQ_segment<int> rmq;
    rmq.init(get_time("24:00:00"));
   
    rep(i,n){
      int res = rmq.query(vec[i].F,vec[i].S);
      rmq.update(vec[i].S-1,res+1);
    }
    cout << rmq.query(0,get_time("24:00:01")) << endl;
  }
  //end = clock();
  //cout << setiosflags(ios::fixed) << setprecision(10) << (double)(end-start)/CLOCKS_PER_SEC << endl;
return 0;
}



/*
Way to check the time of processing speed

clock_t start,end;
start = clock();

------function-------

end = clock();
cout << setiosflags(ios::fixed) << setprecision(10) << (double)(end-start)/CLOCKS_PER_SEC << endl;


*/

C++: #include <bits/stdc++.h>
#define rep(i, start, end) for (long long i = start; i < end; ++i)
#define all(x) (x).begin(), (x).end()
#define len(x) ((long long)(x).size())
#define srt(x) sort((x).begin(), (x).end())
#define rsrt(x) sort((x).rbegin(), (x).rend())
#define g(a, b) __gcd((a), (b))
#define l(a, b) ((a) / __gcd((a), (b)) * (b))
using namespace std;
using ll = long long;
using ld = long double;
using vll = vector<long long>;
using vllvll = vector<vll>;
using vc = vector<char>;
using vs = vector<string>;
using um = unordered_map<long long, long long>;
template<class T>void print(T x) { cout << '\n' << "== " << x << " ==" << '\n'; }
template<class T>void print1d(T x,ll n=-1){if(n==-1)n=x.size();rep(i,0,n){cout<<x[i]<<' ';}cout<<'\n';}
template<class T>void print2d(T x,ll r=-1,ll c=-1){if(r==-1)r=x.size();if(c==-1)c=x[0].size();rep(i,0,r)print1d(x[i],c);}
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
template<class T, class U>T rem(T a, U b) { return a - b*floor(a/b); }
template<class T>ld deg2rad(T deg) { return M_PI * deg / 180.0; }
template<class T>ld rad2deg(T rad) { return 180.0 * rad / M_PI; }
const long double pi = M_PI;
const long double doublepi = M_PI * 2.0;
const long double halfpi = M_PI / 2.0;
const long long big = 1LL << 50;
const long long inf = 1LL << 60;
const long long MOD = 1e9 + 7;



ll sec(ll h, ll m, ll s)
{
    ll res;
    res = h*60*60;
    res += m*60;
    res += s;
    return res;
}

int main()
{
    //cin.tie(0);
    //ios::sync_with_stdio(true);
    ll n = -1;
    ll tmax = sec(24, 0, 0);
    vll res;
    while(true) {
        //puts("here");
        scanf("%lld", &n);
        if (n == 0) break;
        ll h, m, s, hh, mm, ss;
        vll acc(tmax+2, 0);
        rep(i, 0, n) {
            //rewind(stdin);
            scanf("%lld:%lld:%lld %lld:%lld:%lld", &h, &m, &s, &hh, &mm, &ss);
            acc[sec(h,m,s)] += 1;
            acc[sec(hh,mm,ss)] -= 1;
        }

        rep(i, 0, tmax+1) {
            acc[i+1] += acc[i];
        }
        //for (ll el:acc) {
          //  cout << el << ' ';
        //}
        cout << *max_element(all(acc)) << endl;
    }
}