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 <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;
int main(){
  int n;
  while(cin>>n,n){
    vector<pair<string,bool> >v;
    string a,b;
    for(int i=0;i<n;i++){
      cin>>a>>b;
      v.push_back(make_pair(a,1));
      v.push_back(make_pair(b,0));
    }
    sort(v.begin(),v.end());
    int ans=0,k=0;
    string ts;
    for(int i=0;i<v.size();i++){
	if(!k)ts=v[i].first;
	if(v[i].second)k++;
	else k--;
	ans=max(k,ans);
    }
    cout<<ans<<endl;
  }
  return 0;
}

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


#define M  24*60*60
int table[M];


int main(){
  int n;
  int h,m,s;
  string str;
  while(cin >> n, n){

    for(int i = 0; i < n; i++){
      cin >> str;
      scanf("%d:%d:%d", &h,&m,&s);
      int s = h*60*60 + m*60 + s;
      table[s]++;
      scanf("%d:%d:%d", &h,&m,&s);
      int e = h*60*60 + m*60 + s;
      table[e]--;
    }
    for(int i = 1; i < M; i++){
      table[i] += table[i-1];
    }
    int max = 0;
    for(int i = 0; i < M; i++){
      if(max < table[i]) max = table[i];
    }
    cout << max << endl;
  }


}

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

using namespace std;

int main(void) {
    int n;
    while (cin >> n, n) {
        int T[86410] = {};
        for (int i = 0; i < n; i++) {
            int h[2], m[2], s[2], t[2];
            for (int j = 0; j < 2; j++) {
                scanf("%d:%d:%d", &h[j], &m[j], &s[j]);
                t[j] = h[j]  3600 + m[j]  60 + s[j];
                if (!j) T[t[j]]++;
                else T[t[j]]--;
            }
        }

        int ans = 0;
        for (int i = 0; i < 86400; i++) {
            if (i) T[i] += T[i - 1];
            ans = max(ans, T[i]);
        }
        
        cout << ans << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define _GLIBCXX_DEBUG
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define rep1(i, n) for(int i = 1; i < (n); ++i)
using namespace std;
typedef long long ll;

int hms2sec(string hms){
    int h = 10*(hms[0]-'0') + (hms[1]-'0');
    int m = 10*(hms[3]-'0') + (hms[4]-'0');
    int s = 10*(hms[6]-'0') + (hms[7]-'0');

    return 3600*h + 60*m + s;
}

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

    while(1){
        int n;
        cin >> n;

        if(n == 0) break;

        const int DAY = 24 * 60 * 60;

        vector<int> imos(DAY+10);
        rep(i, n){
            string fr_str, to_str;
            cin >> fr_str >> to_str;

            int from = hms2sec(fr_str);
            int to = hms2sec(to_str);

            ++imos[from];
            --imos[to];
        }
        int res = 0;
        rep1(i, DAY+10){
            imos[i] += imos[i-1];
            res = max(res, imos[i]);
        }

        cout << res << endl;

    }

    return 0;
}

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


#define M  24*60*60
int table[M];


int main(){
  int n;
  int h,m,sec;
  string str;
  while(cin >> n, n){

    for(int i = 0; i < n; i++){
      cin >> str;
      scanf("%d:%d:%d", &h,&m,&sec);
      int s = h*60*60 + m*60 + sec;
      table[s]++;
      scanf("%d:%d:%d", &h,&m,&s);
      int e = h*60*60 + m*60 + s;
      table[e]--;
    }
    for(int i = 1; i < M; i++){
      table[i] += table[i-1];
    }
    int max = 0;
    for(int i = 0; i < M; i++){
      if(max < table[i]) max = table[i];
    }
    cout << max << endl;
  }


}

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, 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 sum = 1, wait = 1, ans = 1;
        for(int i = 0; i < 24 * 3600; i++) {
            if(t[i] > 0) {
                if(wait < t[i]) {
                    ans += t[i];
                    sum += t[i];
                } else {
                    wait -= t[i];
                }
            } else if(t[i] < 0) {
                wait -= t[i];
            }
        }
        cout << ans << endl;
    }
}