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

int main(){
	int n;
	cin >> n;
	
	while(n!=0){
		vector<int> train(86405);
		rep(i,n){
			string s1,s2;
			cin >> s1 >> s2;
			int time1 = 0;
			time1 += 3600*(10*(s1[0] - '0') + (s1[1] - '0'));
			time1 += 60*(10*(s1[3] - '0') + (s1[4] - '0'));
			time1 += 10*(s1[6] - '0') + (s1[7] - '0');
			train[time1]++;
			int time2 = 0;
			time2 += 3600*(10*(s2[0] - '0') + (s2[1] - '0'));
			time2 += 60*(10*(s2[3] - '0') + (s2[4] - '0'));
			time2 += 10*(s2[6] - '0') + (s2[7] - '0');
			train[time2]--;
		}
		
		rep(i,86401){
			if(i>0){
				train[i] += train[i-1];
			}
		}
		
		int ans = 0;
		
		rep(i,86401){
			ans = max(ans,train[i]);
		}
		
		cout << ans << endl;
		
		cin >> n;
		
	}
	
	
	
    return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <string>
#include <utility>
#include <vector>
using namespace std;
int main() {
  int n, ans, k;
  string s, t;
  vector< pair<string, int> > T;
  while (cin >> n, n) {
    for (int i = 0; i < n; ++i) {
      cin >> s >> t;
      T.push_back(make_pair(s, 1));
      T.push_back(make_pair(t, -1));
    }
    ans = 0;
    k = 0;
    sort(T.begin(), T.end());
    for (int i = 0; i < 2*n; ++i) {
      k += T[i].second;
      ans = max(ans, k);
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include<bits/stdc++.h>
#define INF 2000000000
#define int long long int
#define MOD 1000000007
#define pb push_back
#define cin1(n) (cin >> n)
#define cin2(a,b) (cin >> a >> b)
#define cin3(a,b,c) (cin >> a >> b >> c)
#define cout(n) (cout << n << endl)
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define fr first 
#define sc second 
#define EPS (1e-10)

using namespace std;

typedef vector<int> vi;
typedef vector< vector<int> > vvi;
typedef vector<pair<int,int>> vpii;
typedef vector<string> vs;
typedef vector<vector<string>> vss;
typedef pair<int,int> pii;

int dx[] = {1,-1,0,0};
int dy[] = {0,0,1,-1};
int n,m;
int a,b;
int p,q;

pii input(string t1,string t2) {
	int ret1,ret2;

	ret1 = stoi(t1.substr(6,2)) + 60 * stoi(t1.substr(3,2)) + 60 * 60 * stoi(t1.substr(0,2));
	ret2 = stoi(t2.substr(6,2)) + 60 * stoi(t2.substr(3,2)) + 60 * 60 * stoi(t2.substr(0,2));
	return make_pair(ret1,ret2);
}

signed main() {

	while(1) {
		cin1(n);
		if (n == 0) break;

		vpii table(n,make_pair(0,0));
		rep(i,0,n) {
			string time1,time2;
			cin2(time1,time2);
			table[i] = input(time1,time2);	
			//cout << table[i].fr << " " << table[i].sc << endl;
		}
		
		int idx = 0;
		vector<pair<bool,int>> train;
		train.pb(make_pair(true,0));
		rep(i,0,60*60*24) {
			//std::cout << "table.fr " << table[idx].fr <<  std::endl;
			rep(j,0,train.size()) {
				if (train[j].sc == i) {
					//cout << "j = " << j << endl;
					//cout << "i = " << i << endl;
					train[j].fr = true;
					train[j].sc = 0;
				}
			}
			if (table[idx].fr == i) {
				//cout << "idx = " << idx << endl;
				//cout << "i = " << i << endl;
				//cout(table[idx].fr);
				bool flag = false;
				rep(j,0,train.size()) {
					if (train[j].fr) {
						train[j].fr = false;
						train[j].sc = table[idx].sc;
						flag = true;
						break;
					}
				}
				if (!flag) {
					train.pb(make_pair(false,table[idx].sc));
				}
				idx++;
				i--;
			}
		}
		cout(train.size());
	}

	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;
    for(int i=0;i<v.size();i++){
	if(v[i].second)k++;
	else k--;
	ans=max(k,ans);
    }
    cout<<ans<<endl;
  }
  return 0;
}

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

using namespace std;

int main() {

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

		if (n == 0) { return 0; }

		vector<struct tm> tms(n);
		vector<struct tm> tme(n);

		string in1, in2;

		vector<int> jikoku(86401);

		for (int i = 0; i < n; i++) {
			cin >> in1 >> in2;

			tms[i].tm_year = 70;
			tms[i].tm_mon = 0;
			tms[i].tm_mday = 1;
			tms[i].tm_hour = stoi(in1.substr(0, 2)) + 9;
			tms[i].tm_min = stoi(in1.substr(3, 2));
			tms[i].tm_sec = stoi(in1.substr(6, 2));

			tme[i].tm_year = 70;
			tme[i].tm_mon = 0;
			tme[i].tm_mday = 1;
			tme[i].tm_hour = stoi(in2.substr(0, 2)) + 9;
			tme[i].tm_min = stoi(in2.substr(3, 2));
			tme[i].tm_sec = stoi(in2.substr(6, 2));


			jikoku[mktime(&tms[i])]++;
			jikoku[mktime(&tme[i])]--;

		}

		int res = 0;
		int resmax = 0;
		for (int i = 0; i < 86401; i++) {
			res += jikoku[i];
			resmax = max(resmax, res);
		}

		cout << resmax << endl;
	}
	return 0;
}