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 debug(x) cerr << #x << ':' << x << endl
#define rep(i,n) for(int i=0;i<(int)n;++i)
#define ALL(c) (c).begin(), (c).end()
using namespace std;
typedef long long ll;

int main(){
    int n;
    // cout << stoi("01") << endl;
    while(1){
        cin >> n;
        if(n==0) break;
        vector<int> T(60*60*60+1,0);
        for(int i=0; i<n; i++){
            string s1, s2;
            cin >> s1 >> s2;
            int from = stoi(s1.substr(0,2))*60*60 + stoi(s1.substr(3,2))*60 + stoi(s1.substr(6,2));
            int to = stoi(s2.substr(0,2))*60*60 + stoi(s2.substr(3,2))*60 + stoi(s2.substr(6,2));
            // cout << "from " << from << " to " <<to << endl;
            T[from] +=1;
            T[to] -= 1;
        }

        rep(i,60*60*60+1){
            T[i+1] += T[i];
            // cout << T[i] << " ";
            // if(i%40==0) cout << endl;
        }
        // cout << endl;
        int ma = -1;
        rep(i,60*60*60+1){
            if(ma < T[i]) ma = T[i];
        }
        cout << ma << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(i = 0;i < n;++i)
#define all(v) v.begin(), v.end()
using ll = long long;

int main()
{
    ll i,j;
    while(true){
        ll n;
        cin >> n;
        if(n == 0) return 0;
        vector<ll> times(1e5,0);
        for(i = 0;i < n;++i){
            string hatsu,tyaku;
            cin >> hatsu >> tyaku;
            ll h1 = (hatsu.at(0) - '0')*10 + (hatsu.at(1) - '0');
            ll m1 = (hatsu.at(3) - '0')*10 + (hatsu.at(4) - '0');
            ll s1 = (hatsu.at(6) - '0')*10 + (hatsu.at(7) - '0');
            ll tmp1 = h1*60*60 + m1*60 + s1;

            ll h2 = (tyaku.at(0) - '0')*10 + (tyaku.at(1) - '0');
            ll m2 = (tyaku.at(3) - '0')*10 + (tyaku.at(4) - '0');
            ll s2 = (tyaku.at(6) - '0')*10 + (tyaku.at(7) - '0');
            ll tmp2 = h2*60*60 + m2*60 + s2;
            ++times.at(tmp1); --times.at(tmp2);
        }
        for(i = 0;i < times.size()-1;++i){
            times.at(i+1) += times.at(i);
        }
        sort(all(times));
        cout << times.back() << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<cmath>
#include<algorithm>
#include<vector>
#include<queue>

using namespace std;

int main(){

  int n;
  cin >> n;

  while(n!=0){
    int s[86401]={};
    for(int i=0;i<n;i++){
      string u,t;
      cin >> u >> t;
      s[stoi(u.substr(0,2))*3600+stoi(u.substr(3,2))*60+stoi(u.substr(6,2))]++;
      s[stoi(t.substr(0,2))*3600+stoi(t.substr(3,2))*60+stoi(t.substr(6,2))]--;
    }

    int m=0;
    for(int i=0;i<86400;i++){
      s[i+1]+=s[i];
      m=max(m,s[i]);
    }

    cout << m << endl;

    cin >> n;
  }

}

C++: #include<iostream>
#define MAX 84400
#include<algorithm>
#include<cstdlib>
#include<vector>
#include<string>
using namespace std;
int main(){
	int n,l,a;
	char s[20];
	vector<int> table;
	while(cin>>n,n){
		int max=0;
		for(int i=0;i<MAX;i++)
		table.push_back(0);
		for(int i=0;i<n;i++){
			cin>>s;
			l=atoi(s)*3600+atoi(&s[2])*60+atoi(&s[6]);
			cin>>s;
			a=atoi(s)*3600+atoi(&s[2])*60+atoi(&s[6]);
			for(int j=l;j<a;j++){
			table[j]++;
			if(table[j]>max)
			max=table[j];
			}
		}
		cout<<max<<endl;
		table.clear();
	}
	return 0;
}

C++: #include <bits/stdc++.h>
#include <stdint.h>

typedef uint32_t u32;
typedef uint64_t u64;
typedef std::pair<int, int> pii;

int t1[20000];
int t2[20000];
bool used[20000];
int n;

void solve(int t) {
  int mini = -1;
  int min = 1000000;
  for(int i = 0; i < n; ++i) {
    if( used[i] ) continue;
    if( t <= t1[i] ) {
      if( min > t1[i] ) {
        min = t1[i];
        mini = i;
      }
    }
  }
  if( mini != -1 ) {
    used[mini] = true;
    solve(t2[mini]);
  }
  return;
}
  
int main() {

  for(;;) {
    int h1, m1, s1, h2, m2, s2;
    scanf("%d", &n);
    if( n == 0 ) break;
    for(int i = 0; i < n; ++i) {
      scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
      t1[i] = h1 * 3600 + m1 * 60 + s1;
      t2[i] = h2 * 3600 + m2 * 60 + s2;
    }
    for(int i = 0; i < n; ++i) used[i] = false;
    int res = 0;
    for(;;) {
      for(int i = 0; i < n; ++i) {
        if( not used[i] ) {
          solve(0);
          res += 1;
          goto label_1;
        }
      }
      break;
    label_1:;
    }
    std::cout << res << std::endl;
  }      

  return 0;
}