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 <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;
		
		v[start]++;
		v[end]--;
	}
	int ans = 0;
	int now = 0;
	rep(i, 86410){
		now += v[i];
		ans = max(ans, now);
	}
	printf("%d\n", ans);
}
int main(void){
	rep(i, 1000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

C++: #include <bits/stdc++.h>
#define For(i, a, b) for(int (i)=(int)(a); (i)<(int)(b); ++(i))
#define rFor(i, a, b) for(int (i)=(int)(a)-1; (i)>=(int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<int, lint> pil;
typedef pair<lint, lint> pll;
template<class T> bool chmax(T &a, const T &b){if(a<b){a=b; return true;} return false;}
template<class T> bool chmin(T &a, const T &b){if(a>b){a=b; return true;} return false;}
template<class T> T div_floor(const T a, const T b){return a>=0 ? a/b : (a+1)/b-1;}
template<class T> T div_ceil(const T a, const T b){return a>=0 ? (a-1)/b+1 : a/b;}

constexpr lint mod = 1e9+7;
constexpr lint INF = mod*mod;
constexpr int MAX = 100010;

int main(){
    int n;
    using time = tuple<int, int, int>;
    using train = pair<time, time>;
    while(scanf("%d", &n) && n){
        multiset<train> S;
        rep(i, n){
            int h1, m1, s1, h2, m2, s2;
            scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
            S.insert({make_tuple(h1, m1, s1), make_tuple(h2, m2, s2)});
        }
        int ans = 0;
        while(!S.empty()){
            ++ans;
            int h, m, s;
            tie(h, m, s) = (*S.begin()).se;
            S.erase(S.begin());
            while(true){
                auto it = S.lower_bound({make_tuple(h, m, s), make_tuple(0, 0, 0)});
                if(it == S.end()) break;
                tie(h, m, s) = (*it).se;
                S.erase(it);
            }
        }
        printf("%d\n", ans);
    }
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <cstdio>
using namespace std;
#define rep(i,a) for(int i = 0 ; i < a ; i ++)
int main(void){
  int n;
  while(cin>>n,n){
    vector<int> ary(24*60*60,0);
    char b[9],e[9];
    while(n--){
      cin>>b>>e;
      int h,m,s;
      sscanf(b,"%d:%d:%d",&h,&m,&s);
      int start = ((h * 60) + m) * 60 + s; 
      sscanf(e,"%d:%d:%d",&h,&m,&s);
      int finish = ((h * 60) + m) * 60 + s; 
      for(int i = start + 1 ; i < finish ; i ++)ary[i]++;
    }
    int ret = -1;
    for(int i = 0 ; i < ary.size() ; i ++)ret = max(ret,ary[i]);
    cout<<ret<<endl;
  }
}

C++: #include <cstdio>
#include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;

int main()
{
    for(;;){
        int n;
        cin >> n;
        if(n == 0)
            return 0;

        vector<vector<int> > t(2, vector<int>(n));
        for(int i=0; i<n; ++i){
            for(int j=0; j<2; ++j){
                int h, m, s;
                char c;
                cin >> h >> c >> m >> c >> s;
                t[j][i] = (h * 60 + m) * 60 + s;
            }
        }

        int ret = 0;
        vector<bool> check(n, false);
        for(int i=0; i<n; ++i){
            if(!check[i])
                ++ ret;
            for(int j=i+1; j<n; ++j){
                if(t[0][j] >= t[1][i] && !check[j]){
                    check[j] = true;
                    break;
                }
            }
        }
        cout << ret << endl;
    }
}

C++: #include<stdio.h>
#include<iostream>
using namespace std;

int main(){

int n,q;
int h1=0,m1=0,s1=0,h2=0,m2=0,s2=0;
while(1){
cin>>n;if(n==0)break;
long long int N[90800]={};
for(int i=0;i<n;i++)
{scanf("%d:%d:%d",&h1,&m1,&s1);
scanf("%d:%d:%d",&h2,&m2,&s2);
long int L1=h1*3600+m1*60+s1;
long int L2=h2*3600+m2*60+s2;
for(int j=L1;j<L2;j++)
	N[j]++;
}
int max=0;
for(int i=0;i<=90800;i++)
{if(N[i]>max)max=N[i];}
cout<<max<<endl;
}
return 0;
}