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 <cstdio>
#include <algorithm>
using namespace std;

const int TIME = 60 * 60 * 24 + 60;
int data[TIME];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	while(cin >> n && n){
		fill(data, data + TIME, 0);
		
		int a, b, c;
		for(int i = 0; i < n; ++i){
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] ++;
			
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] --;
		}
	
		int ans = 0;
		for(int i = 0; i < TIME; ++i){
			if(i > 0)
				data[i] += data[i - 1];
			ans = max(ans, data[i]);
		}
		
		cout << ans << endl;
	}
	return 0;
}

C++: #include "bits/stdc++.h"
using namespace std;
int train[24*60*60+1];
int main() {
	int n;
	while(scanf("%d",&n),n) {
		memset(train,0,sizeof(train));
		for(int i=0;i<n;i++) {
			int hh,mm,ss;
			scanf("%d:%d:%d",&hh,&mm,&ss);
			int l=hh*60*60+mm*60+ss;
			scanf("%d:%d:%d",&hh,&mm,&ss);
			int r=hh*60*60+mm*60+ss;
			train[l]++;
			train[r]--;
		}
		int ans=0;
		for(int i=0;i<24*60*60;i++) {
			train[i+1]+=train[i];
			ans=max(ans,train[i]);
		}
		printf("%d\n",ans);
	}
}

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

typedef long long ll;

ll f(string s){
    string s1,s2,s3;
    s1 = s.substr(0,2);
    s2 = s.substr(3,2);
    s3 = s.substr(6,2);

    int hh = stoi(s1)*3600;
    int mm = stoi(s2)*60;
    int ss = stoi(s3)*1;

    return hh+mm+ss;
}

const int mx=23*3600+59*60+59;

void solve(int n){
    vector<int> v(mx+10,0);
    for(ll i=0;i<n;i++){
        string s1,s2;
        cin >> s1 >> s2;
        ll s=f(s1);
        ll t=f(s2);
        v[s]++;
        v[t]--;
    }
    for(int i=1;i<mx+10;i++){
        v[i] = v[i] + v[i-1];
    }
    int ans = 0;
    for(int i=0;i<mx+10;i++){
        ans = max(ans,v[i]);
        if(v[i] == 6)  cout << i << endl;
    }
    cout << ans << endl;
}

int main(){
    int n;
    while(cin>>n){
        if(n==0) break;
        solve(n);
    }
}

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

const int TIME = 60 * 60 * 24 + 60 * 60 + 60;
int data[TIME];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	while(cin >> n && n != 0){
		for(int i = 0; i < TIME; ++i){
			data[i] = 0;
		}
		
		int a, b, c;
		for(int i = 0; i < n; ++i){
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] ++;
			
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 60 * 60 + b * 60 + c] --;
		}
	
		int ans = 0;
		for(int i = 0; i < TIME; ++i){
			if(i > 0)
				data[i] += data[i - 1];
			ans = max(ans, data[i]);
		}
		
		cout << ans << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>

#define CH(N,A,B) (A<=N&&N<B)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define RREP(i,a,b) for(int i=(b-1);a<=i;i--)

using namespace std;

int d[10000000], n, hhS, mmS, ssS, hhG, mmG, ssG;

int main() {
  while(1){
    cin>>n;
    if(n==0) break;
    REP(i,1,24*60*60+1) d[i] = 0;
    REP(i,0,n){
      scanf("%d:%d:%d %d:%d:%d", &hhS, &mmS, &ssS, &hhG, &mmG, &ssG);
      d[hhS*(60*60) + mmS*60 + ssS]++;
      d[hhG*(60*60) + mmG*60 + ssG]--;
      //test
      //cout<<"hhS "<<hhS<<", hhG "<<hhG<<endl;
    }
    int ans = 0;
    REP(i,1,24*60*60+1){
      d[i] += d[i-1];
      ans = max(ans, d[i]);
    }
    cout<<ans<<endl;
  }

  return 0;
}