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 <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
typedef pair<int, int> P;
typedef pair<int, P> PP;
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  while(cin>>n,n) {
    priority_queue<PP, vector<PP>, greater<PP> > Q;
    int ans = 0;
    FOR(i,0,n) {
      int h1, m1, s1; scanf("%d:%d:%d",&h1,&m1,&s1);
      int h2, m2, s2; scanf("%d:%d:%d",&h2,&m2,&s2);
      if(Q.empty()) {
        ans++;
        Q.push(PP(h2, P(m2, s2)));
      } else {
        PP pp = Q.top();
        int h = pp.first;
        int m = pp.second.first;
        int s = pp.second.second;
        if(h1 == h) {
          if(m1 == m) {
            // ?????????
            if(s1 >= s) {
              Q.pop();
              Q.push(PP(h2, P(m2, s2)));
            } else {
              ans++;
              Q.push(PP(h2, P(m2, s2)));
            }
          } else {
            // ?????????
            if(m1 >= m) {
              Q.pop();
              Q.push(PP(h2, P(m2, s2)));
            } else {
              ans++;
              Q.push(PP(h2, P(m2, s2)));
            }
          }
        } else {
          if(h1 >= h) {
            Q.pop();
            Q.push(PP(h2, P(m2, s2)));
          } else {
            ans++;
            Q.push(PP(h2, P(m2, s2)));
          }
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)

void slove(int n){
	vector<int> v(86410);
	rep(i, 86410) v[i] = 0;//?????????
	rep(i, n){
		string s, e;
		cin >> s >> e;
		//?§???°?????????
		int start = 36000 * (s[0] - '0') + 3600 * (s[1] - '0') 
					+ 600 * (s[3] - '0') + 60 * (s[4] - '0')
					+ 10 * (s[6] - '0') + 1 * (s[7] - '0');
		int end = 36000 * (e[0] - '0') + 3600 * (e[1] - '0') 
					+ 600 * (e[3] - '0') + 60 * (e[4] - '0')
					+ 10 * (e[6] - '0') + 1 * (e[7] - '0') - 1;
		printf("%d %d\n", start, end);
		for (int j = start; j <= end ; ++j) v[j]++;//???????????????
	}
	sort(all(v));
	reverse(all(v));
	printf("%d\n", v[0]);
}
int main(void){
	rep(i, 1000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

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

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(v) v.begin(),v.end()
#define _GLIBCXX_DEBUG

using ll = long long;
using vi = vector<int>;
using vll = vector<ll>;
using vd = vector<double>;
using vvi = vector<vi>;
using vvll = vector<vll>;
using vvd = vector<vd>;
using vvvi = vector<vvi>;
using vvvll = vector<vvll>;
using vvvd = vector<vvd>;

const double pi=acos(-1);
const ll MOD=1e9+7;
const ll INF=(1LL<<60);

int to_int(string w){
    int num1=10*(w[0]-'0')+w[1]-'0';
    int num2=10*(w[3]-'0')+w[4]-'0';
    int num3=10*(w[6]-'0')+w[7]-'0';
    return 3600*num1+60*num2+num3;
}

int main() {
    while(1){
        int n;
        cin>>n;
        if(n==0)return 0;
        vi d(3600*24+1,0);
        rep(i,n){
            string w1,w2;
            cin>>w1>>w2;
            int t1=to_int(w1),t2=to_int(w2);
            //cout<<t1<<" "<<t2<<endl;
            d[t1]+=1;
            d[t2]-=1;
        }
        int ans=0;
        int now=0;
        rep(i,3600*24){
            now+=d[i];
            ans=max(ans,now);
        }
        cout<<ans<<endl;
    }
    

    return 0;
}

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

using namespace std;

typedef pair<int, int> P;

int main() {
	int n;
	char d;
	while(cin>>n) {
		if(n == 0){
			break;
		}
		vector<P> t(n);
		int h[2],m[2],s[2];
		for(int i= 0;i < n;i++){
			cin >> h[0]>> d >> m[0] >> d >> s[0] >> h[1] >> d >>m[1]>> d >>s[1];
			t[i].first= h[0]*3600+m[0]*60+s[0];
			t[i].second= h[1]*3600+m[1]*60+s[0];
		}
		for (int i =n-1; i> 0; i--) {
			for (int j =0; j < i; j++){
				if (t[j].first > t[j+1].first) {
					swap(t[j], t[j+1]);
				} else if (t[j].first == t[j+1].first){
					if (t[j].second > t[j+1].second) {
						swap(t[j], t[j+1]);
					}
				}
			}
		}
		queue<P> t1;
		priority_queue<int, vector<int>, greater<int> > t2;
		for (int i=0; i< n; i++) {
			t1.push(t[i]);
		}
		int train =0;
		P p = t1.front();
		t1.pop();
		t2.push(p.second);
		train++;
		for (int i= 1; i < n; i++){
			p = t1.front();
			t1.pop();
			if (!t2.empty() && t2.top() <= p.first) {
				t2.pop();
			} else {
				train++;
			}
			t2.push(p.second);
		}
		cout<<train << endl;
	}
	return 0;
}