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

int main(){
	int n,x,y,z,res,ans;
	int a[24][60][60],b[24][60][60];
	char c1,c2;
	string s1,s2;
	while(1){
		cin >> n;
		if(n == 0)break;
		for(int i = 0;i < 24;i++){
			for(int j = 0;j < 60;j++){
				for(int k = 0;k < 60;k++){
					a[i][j][k] = b[i][j][k] = 0;
				}
			}
		}
		for(int i = 0;i < n;i++){
			cin >> s1 >> s2;
			istringstream iss1(s1);
			iss1 >> x >> c1 >> y >> c2 >> z;
			//cout << x <<" " << y << " " << z <<endl; 
			a[x][y][z]++;
			istringstream iss2(s2);
			iss2 >> x >> c1 >> y >> c2 >> z;
			b[x][y][z]++;
		}
		res = 0;
		ans = 0;
		for(int i = 0;i < 24;i++){
			for(int j = 0;j < 60;j++){
				for(int k = 0;k < 60;k++){
					if(b[i][j][k] != 0){
						res -= b[i][j][k];
					}
					if(a[i][j][k] != 0){
						res += a[i][j][k];
						ans = max(ans,res);
					}
				}
			}
		}
		cout << ans <<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

int n;
int dif[90000], sum[90000];
int S[10005], T[10005];

int gettime()
{
  string tmp;
  char c; int ret = 0;

  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 3600;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 60;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str());

  return ret;
}

int main(void)
{
  while(1){
    cin >> n;
    if(n == 0) break;

    for(int i = 0; i <= 86405; i++) dif[i] = 0;

    for(int i = 0; i < n; i++){
      S[i] = gettime();
      T[i] = gettime();
    }

    /*for(int i = 0; i < n; i++){
      cout << S[i] << " " << T[i] << endl;;
    }*/

    for(int i = 0; i < n; i++){
      dif[S[i]]++;
      dif[T[i]]--;
    }
    sum[0] = dif[0];
    for(int i = 1; i <= 86405; i++){
      sum[i] = sum[i-1] + dif[i];
    }

    int ans = 0;
    for(int i = 0; i <= 86405; i++){
      ans = max(ans, sum[i]);
    }
    cout << ans << endl;
  }

  return 0;
}

C++: #include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define INF 1000000000
#define rep(i,a,b) for (int i=(a);i<(b);i++)
#define rev(i,a,b) for (int i=(a)-1;i>=b;i--)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef queue<int> qi;
typedef vector<int> vi;
typedef vector<string> vs;
int dx[4] = { 0, 1, 0, -1 };
int dy[4] = { 1, 0, -1, 0 };

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	while(true) {
		int n;
		cin >> n;
		if(n == 0) break;

		vector<pii> vp;
		rep(i,0,n) {
			int h,m,s;
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, 1));
			scanf("%d:%d:%d", &h, &m, &s);
			vp.push_back(pii(h*3600 + m*60 + s, -1));
		}

		sort(vp.begin(), vp.end());

		int ans = 0, tmp = 0;
		rep(i,0,vp.size()) {
			tmp += vp[i].second;
			ans = max(ans, tmp);
		}
		cout << ans << endl;
	}

	return 0;
}

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

#define pb(n) push_back(n)
#define fi first
#define se second
#define all(r) begin(r),end(r)
#define vmax(ary) *max_element(all(ary))
#define vmin(ary) *min_element(all(ary))
#define debug(x) cout<<#x<<": "<<x<<endl
#define fcout(n) cout<<fixed<<setprecision((n))
#define scout(n) cout<<setw(n)
#define vary(type,name,size,init) vector< type> name(size,init)
#define vvl(v,w,h,init) vector<vector<ll>> v(w,vector<ll>(h,init))
#define mp(a,b) make_pair(a,b)

#define rep(i,n) for(int i = 0; i < (int)(n);++i)
#define REP(i,a,b) for(int i = (a);i < (int)(b);++i)
#define repi(it,array) for(auto it = array.begin(),end = array.end(); it != end;++it)
#define repa(n,array) for(auto &n :(array))

using ll = long long;
using pii = pair<int,int> ;
using pll = pair<ll,ll> ;

template<typename T>
void O(T t){
  cout << t << endl;
}

const ll mod = 1e9+7;
constexpr ll inf = ((1<<30)-1)*2+1 ;
constexpr double PI = acos(-1.0) ;
double eps = 1e-10 ;
const int dy[] = {-1,0,1,0,1,-1,1,-1};
const int dx[] = {0,-1,0,1,1,-1,-1,1};

inline bool value(int x,int y,int w,int h){
  return (x >= 0 && x < w && y >= 0 && y < h);
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll n;
  while(cin >> n,n){
    vector<pair<string,string>> s(n);
    rep(i,n){
      cin >> s[i].fi >> s[i].se;
    }
    int c = 1;
    sort(all(s));
    vector<string> t;
    t.push_back(s[0].se);
    rep(i,n-1){
      bool f = false;
      rep(j,t.size()){
        if(s[i+1].fi >= t[j]){
          f = true;
        }
      }
      if(!f){
        ++c;
        t.push_back(s[i+1].se);
      }
    }
    std::cout << c << std::endl;
  }
  return 0;
}