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;

int read(){
    int h, m, s;
    char c;
    cin >> h >> c >> m >> c >> s;
    return 3600*h + 60*m + s;
}

int main(){
    int n;

    while(true){
        cin >> n;
        if(n == 0) break;
        vector<pair<int, int>> timetable;
        for(int i=0;i<n;i++){
            timetable.emplace_back(read(), 1);
            timetable.emplace_back(read(), -1);
        }
        sort(timetable.begin(), timetable.end());
        int max_train = 0;
        int train = 0;
        for(auto t:timetable){
            train += t.second;
            max_train = max(max_train, train);
        }
        cout << max_train << "\n";
    }


    return 0;
}

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

int main () {
    int n;
    while (cin >> n, n) {
        vector<int> start_secs, end_secs;
        for (int i = 0; i < n; i++) {
            char c;
            int hh, mm, ss;
            cin >> hh >> c >> mm >> c >> ss;
            int sec = hh * 3600 + mm * 60 + ss;
            start_secs.push_back(sec);
            cin >> hh >> c >> mm >> c >> ss;
            sec = hh * 3600 + mm * 60 + ss;
            end_secs.push_back(sec);
        }
        sort(start_secs.begin(), start_secs.end());
        sort(end_secs.begin(), end_secs.end());

        int i = 0, j = 0, counter = 0, result = 0;
        while (i < n && j < n) {
            int start_sec = start_secs[i];
            int end_sec = end_secs[j];
            if (start_sec < end_sec) {
                counter++;
                result = max(result, counter);
                i++;
            } else {
                counter--;
                j++;
            }
        }
        cout << result << endl;
    }
}

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

using namespace std;

int n;
int dif[90000], sum[90000];
int S[10005], T[10005];

int gettime()
{
  string tmp;
  char c; int ret = 0;

  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 3600;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 60;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str());

  return ret;
}

int main(void)
{
  while(1){
    cin >> n;
    if(n == 0) break;

    for(int i = 0; i <= 86405; i++) dif[i] = 0;

    for(int i = 0; i < n; i++){
      S[i] = gettime();
      T[i] = gettime();
    }

    /*for(int i = 0; i < n; i++){
      cout << S[i] << " " << T[i] << endl;;
    }*/

    for(int i = 0; i < n; i++){
      dif[S[i]]++;
      dif[T[i]]--;
    }
    sum[0] = dif[0];
    for(int i = 1; i <= 86405; i++){
      sum[i] = sum[i-1] + dif[i];
    }

    int ans = 0;
    for(int i = 0; i <= 86405; i++){
      if(sum[i] == 6) cout << i << endl;
      ans = max(ans, sum[i]);
    }
    cout << ans << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
#define M 1e7
using namespace std;
int main(){
	int n,i,b[6];
	while(cin>>n&&n){
		j=n;
		int a[86400]={0},ans=0,c=0;
		while(n--){
			scanf("%d:%d:%d %d:%d:%d",&b[0],&b[1],&b[2],&b[3],&b[4],&b[5]);
			a[b[0]*3600+b[1]*60+b[2]]++;
			a[b[3]*3600+b[4]*60+b[5]]--;
		}
		for(i=0;i<86400;i++){
			c+=a[i];
			ans=max(ans,c);
		}
		cout<<ans<<endl;
	}
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>
#include <fstream>
#include <bitset>
#include <time.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef complex<double> Point;

#define PI acos(-1.0)
#define EPS 1e-10
const ll INF = (1LL << 31) - 1;
const ll MOD = 1e9 + 7;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,N) for(int i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define EQ(a,b) (abs((a)-(b))<EPS)
#define EQV(a,b) ( EQ((a).real(), (b).real()) && EQ((a).imag(), (b).imag()) )
#define fi first
#define se second
#define N_SIZE (1LL << 20)
#define NIL -1
#define MAX_N 100100 * 3

int n;
ll sum[100100];

int main() {
	while (cin >> n&&n) {
		fill(sum, sum + 100100, 0);
		REP(i, n) {
			char c;
			int h, m, s;
			cin >> h >> c >> m >> c >> s;
			sum[h * 60 * 60 + m * 60 + s]++;
			cin >> h >> c >> m >> c >> s;
			sum[h * 60 * 60 + m * 60 + s - 1]--;
		}
		ll ans = 1;
		REP(i, 100100) {
			sum[i + 1] += sum[i];
			ans = max(ans, max(sum[i + 1], sum[i]));
		}
		cout << ans << endl;
	}
}