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 "random"
#include "ctime"
#include "chrono"
#include "string"
#include "bitset"
#include "algorithm"
#include "map"

using namespace std;


int main() {
	int N;
	cin >> N;
	while (N) {
		vector<pair<string, string>>v(N);
		for (int i = 0; i < N; i++) {
			cin >> v[i].first >> v[i].second;
		}
		map<string, int>m;
		sort(v.begin(), v.end());
		int ans = 0;
		for (auto i : v) {
			if (m.empty()) {
				m[i.second]++;
				ans++;
				continue;
			}
			if ((*m.begin()).first <= i.first) {
				m[(*m.begin()).first]--;
				if ((*m.begin()).second == 0) {
					m.erase(m.begin());
				}
			}
			else {
				m[i.second]++;
				ans++;
			}
		}
		cout << ans << endl;
		cin >> N;
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<string>
#include<cstdio>
#include<cstring>

#define REP(i,n) for(int i=0;i<(n);i++)

int di[4] = {1, 0, -1, 0};
int dj[4] = {0, 1, 0, -1};
using namespace std;

typedef long long ll;
typedef pair<int, int> P;
const ll INF = 1e18;

int table[86400];

int convert2sec(int hh, int mm, int ss){
    return 3600*hh + 60*mm + ss;
}

int main(){
    int n;
    while(cin >> n && n != 0){
        memset(table,0,sizeof(table));
        REP(i,n){
            int hd, md, sd, ha, ma, sa;
            scanf("%d:%d:%d %d:%d:%d", &hd, &md, &sd, &ha, &ma, &sa);
            int dep_sec = convert2sec(hd,md,sd);
            int arr_sec = convert2sec(ha,ma,sa);
            table[dep_sec]++;
            table[arr_sec]--;
        }
        REP(i,86400) if(i>0) table[i] += table[i-1];

        int m = 0;
        REP(i,86400) if(table[i] > m) m = table[i];
        cout << m << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <map>
using namespace std;

typedef pair< int, int > iP;

int main() {

    int n;

    while(cin >> n, n) {
        vector< iP > v;
        vector< int > t(24 * 3600 + 3600 + 61, 0);
        for(int i = 0; i < n; i++) {
            int h, m, s, hh, mm, ss;
            scanf("%2d:%2d:%2d %2d:%2d:%2d", &h, &m, &s, &hh, &mm, &ss);
            v.push_back(iP(h * 3600 + m * 60 + s, hh * 3600 + mm * 60 + ss));
            t[v[v.size() - 1].first]++, t[v[v.size() - 1].second]--;
        }

        int wait = 0, ans = 0;
        for(int i = 0; i < 24 * 3600 + 3600 + 61; i++) {
            if(t[i] > 0) {
                if(wait <= 0) {
                    ans++;
                } else {
                    wait--;
                }
            } else if(t[i] < 0) {
                wait++;
            }
        }
        cout << ans << endl;
    }
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>

using namespace std;

#define FOR(i,k,n) for(int i=(k); i<(int)n; ++i)
#define REP(i,n) FOR(i,0,n)
#define FORIT(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
typedef pair<int,int> P;
int tosc(int h, int m,int s){
  return h*3600 + m * 60 + s;
}

int main(){
  int n;
  while(cin>>n,n){
    vector<P> v;
    REP(i,n){
      int h,m,s;
      scanf("%d:%d:%d",&h,&m,&s);
      int m1 = tosc(h,m,s);
      scanf("%d:%d:%d",&h,&m,&s);
      int m2 = tosc(h,m,s);
      v.push_back(make_pair(m1,m2));
    }
    int ans = 0;
    priority_queue<int, vector<int>, greater<int> > que;
    REP(i,n){
      if(que.empty() || que.top() > v[i].first){
        ans++;
      }else{
        que.pop();
      }
      que.push(v[i].second);
    }
    cout<<ans<<endl;
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <algorithm>

using namespace std;

int main() {
  while (true) {
    vector<int> imos(24 * 60 * 60);
    int n;
    cin >> n;
    if (n == 0) {
      break;
    }
    
    for (int i = 0; i < n; i++) {
      string str1, str2;
      cin >> str1 >> str2;
      int t1, t2;
      t1 = ((str1[0] - '0') * 10 + str1[1] - '0') * 3600 +
           ((str1[3] - '0') * 10 + str1[4] - '0') * 60 +
            (str1[6] - '0') * 10 + str1[7] - '0';
      t2 = ((str2[0] - '0') * 10 + str2[1] - '0') * 3600 +
           ((str2[3] - '0') * 10 + str2[4] - '0') * 60 +
            (str2[6] - '0') * 10 + str2[7] - '0';

      imos[t1]++;
      imos[t2]--;
    }
    int ans = 0;
    for (int i = 1; i < 24 * 60 * 60; i++) {
      imos[i] += imos[i - 1];
      ans = max(ans, imos[i]);
    }

    cout << ans << endl;
  }
  
  return 0;
}

C++: #include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
#include <set>
using namespace std;

#define rep(i,n) for(int i=0;i<(n);i++)
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define dbg(x) cout<<#x"="<<x<<endl

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<pii, int> ppi;

#define INF 1000000000

int main(){
  vector<int> v(24*60*60);

  while(true){
    int n;
    cin >> n;

    if(n==0) break;

    rep(i,24*60*60) v[i]=0;

    int h,m,s;
    rep(i,n){
      scanf("%d:%d:%d", &h, &m, &s);// dbg(h);dbg(m);dbg(s);
      int t1 = (h*24+m)*60+s;
      scanf("%d:%d:%d", &h, &m, &s);// dbg(h);dbg(m);dbg(s);
      int t2 = (h*24+m)*60+s;
      v[t1]++;
      v[t2+1]--;
    }

    int current=0, res=0;
    rep(i, 24*60*60){
      current += v[i];
      res = max(res, current);
    }

    cout << res << endl;
  }
}