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>
#include <vector>
#include <string>
#include <sstream> 
using namespace std;

int n=0;
int buri[86401];
string unko;

int main(){
    while(true){
        cin>>n;
        if(n==0){
            return 0;
        }
        else{
            for(int i=0; i<=86400; i++){
                buri[i]=0;
            }
            for(int i=0; i<n; i++){
                int j,h,b,j2,h2,b2;
                scanf("%d:%d:%d %d:%d:%d",&j,&h,&b,&j2,&h2,&b2);
                int tmp1=j*3600+h*60+b;
                int tmp2=j2*3600+h2*60+b2;
                //cout<<tmp1<<tmp2;
                for(int ii=tmp1; ii<tmp2; ii++){
                    buri[ii]++;
                }
            }

            int max=0;
            for(int i=0; i<=86400; i++){
                max=std::max(max,buri[i]);
            }
            cout<<max<<endl;
        }
    }
}




/*

std::vector<std::string> StringSplit(const std::string &str, char sep)
{
    std::vector<std::string> v;
    std::stringstream ss(str);
    std::string buffer;
    while( std::getline(ss, buffer, sep) ) {
        v.push_back(buffer);
    }
    return v;
}
*/

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
void solve();
main { solve(); return 0; }
// clang-format on

void solve() {
  int n;
  while (cin >> n, n) {
    vpii v(n);
    rep(i, n) {
      int h, m, d;
      char gomi;
      cin >> h >> gomi >> m >> gomi >> d;
      int l = h * 60 * 60 + m * 60 + d;
      cin >> h >> gomi >> m >> gomi >> d;
      int r   = h * 60 * 60 + m * 60 + d;
      v[i].fi = l;
      v[i].se = r;
    }
    priority_queue<int, vector<int>, greater<int>> q;
    q.push(v[0].se);
    loop(i, 1, n) {
      if (q.top() <= v[i].fi) q.pop();
      q.push(v[i].se);
    }
    cout << q.size() << endl;
  }
}

C++: #include<cstdio>
#include<cstring>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
typedef pair<int,int> P;
int n;
int S[10001],E[10001];
int f[216005];
int main(){
  while(scanf("%d",&n),n){
    memset(f,0,sizeof(f));
    for(int i=0;i<n;i++){
      int s1,h1,m1,s2,h2,m2;
      scanf("%d:%d:%d %d:%d:%d",&h1,&m1,&s1,&h2,&m2,&s2);
      S[i]=h1*3600+m1*60+s1;
      E[i]=h2*3600+m2*60+s2;
      for(int j=S[i];j<E[i];j++) f[j]++;
    }
    int res=0;
    for(int i=0;i<216000;i++){
      res = max(res,f[i]);
    }
    printf("%d\n",res);
  }
}