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 <iostream>
#include <limits.h>
#include <math.h>
#include <set>
#include <stack>
#include <stdlib.h>
#include <string>
#include <vector>

#define el endl
#define fd fixed
#define INF INT_MAX/2-1
#define pb push_back

using namespace std;

int main() {
  int n, dh, dm, ds, ah, am, as, dtime, atime;
  string dep, arr, num = "0123456789";
  while (cin >> n, n) {
    int cnt[24*60*60] = {0};
    while (n--) {
      cin >> dep >> arr;
      dh = (int)num.find(dep[0])*10 + (int)num.find(dep[1]);
      dm = (int)num.find(dep[3])*10 + (int)num.find(dep[4]);
      ds = (int)num.find(dep[6])*10 + (int)num.find(dep[7]);
      ah = (int)num.find(arr[0])*10 + (int)num.find(arr[1]);
      am = (int)num.find(arr[3])*10 + (int)num.find(arr[4]);
      as = (int)num.find(arr[6])*10 + (int)num.find(arr[7]);
      dtime = (dh*60+dm)*60+ds;
      atime = (ah*60+am)*60+as;
      for (int i = dtime; i < atime; i++) {
        cnt[i]++;
      }
    }
    int max = 0;
    for (int i = 0; i < 24*60*60; i++) {
      if (max < cnt[i]) {
        max = cnt[i];
      }
    }
    cout << max << el;
  }
}

C++: #include<iostream>
#include<cstdio>
using namespace std;
int a[24 * 60 * 60];
int main() {
	long long a1, m1, a2, m2, a3, m3;
	int n;
	while (cin >> n&&n != 0) {
		int h1, m1, s1, h2, m2, s2;
		fill(a, a + 60 * 24 * 60, 0);
		int sum = 0;
		for (int i = 0; i<n; i++) {
			scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
			if (a[h1 * 3600 + m1 * 60 + s1] == 0) {
				sum++;
				for (int i = 0; i<24 * 60 * 60; i++) a[i]++;
			}
			for (int i = h1 * 3600 + m1 * 60 + s1; i<=h2 * 3600 + m2 * 60 + s2; i++) {
				a[i]--;
			}
			a[h2 * 3600 + m2 * 60 + s2]++;
		}
		cout << sum << endl;
	}
}

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

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

using namespace std;
typedef long long ll;

int main()
{
    int n;
    while(cin >> n && n) {

        vector<string> v;

        vector<pair<string,string> > res;
        rep(i,n) {
            string s,t;
            cin >> s >> t;
            res.push_back(make_pair(s,t));
        }
        sort(res.begin(),res.end());
        
        v.push_back(res[0].second);

        REP(i,1,n) {
            string s = res[i].first;
            string t = res[i].second;

            bool flag = true;

            rep(j,v.size()) {
                if(v[j] <= s) {
                    v[j] = t;
                    flag = false;
                    break;
                }
            }

            if(flag) v.push_back(t);
        }

        cout << v.size() << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <map>
#include <algorithm>
using namespace std;
typedef pair<int, int> P;
bool comp(const P p1, const P p2){return p1.first < p2.first;}
int N;
P G[10000];
int solve(){
  int res = 0;
  for (int i = 0; i < N; i++){
    int cnt = 0;
    for (int j = 0; j < N; j++){
      if (G[j].first >= G[i].second){
	break;
      }
      if(G[j].second > G[i].first){
	cnt++;
      }
    }
    res = max(cnt, res);
  }
  return res;
}
int main(){
  while (1){
    cin >> N;
    if (N == 0) break;
    for (int i = 0; i < N; i++){
      char str[10];
      cin >> str;
      int a = (str[0]-'0')*10 + str[1]-'0';
      int b = (str[3]-'0')*10 + str[4]-'0';
      int c = (str[6]-'0')*10 + str[7]-'0';
      G[i].first = a*10000 + b*100 + c;
      
      cin >> str;
      a = (str[0]-'0')*10 + str[1]-'0';
      b = (str[3]-'0')*10 + str[4]-'0';
      c = (str[6]-'0')*10 + str[7]-'0';
      G[i].second = a*10000 + b*100 + c;
    }
    sort (G, G+N, comp);
    cout << solve() << endl;
  }
}

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

#define rep(i,n) for(int i=0; i<n; i++)
int num[24*60*60]; //??????????§?????????£???????????°??°

int main(){
  int n;
  while(cin>>n, n!=0){
    rep(i,24*60*60)num[i]=n;
    rep(i,n){
      int sh, sm, ss, eh, em, es;
      scanf("%2d:%2d:%2d %2d:%2d:%2d", &sh, &sm, &ss, &eh, &em, &es);
      for(int j=(sh*24*60)+(sm*60)+ss; j<(eh*24*60)+(em*60)+es; j++)
	num[j]--;
    }
    int mini=n;
    for(int i=0; i<24*60*60; i++)
      if(mini>num[i])mini=num[i];
    cout<<n-mini<<endl;
  }
  return 0;
}

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

int main(){
	int n;
	while(cin >> n,n){
		int cnt[100000] = {},ma = 0;
		for(int i = 0;i < n;i++){
			int a,b,c,d,e,f;
			scanf("%d:%d:%d %d:%d:%d",&a,&b,&c,&d,&e,&f);
			cnt[a * 3600 + b * 60 + c + 1]++;
			cnt[d * 3600 + e * 60 + f + 1]--;
		}
		for(int i = 1;i <= 86400;i++){
			cnt[i] += cnt[i - 1];
			ma = max(ma,cnt[i]);
		}
		cout << ma << endl;
	}
}