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<algorithm>
using namespace std;

#define DAY_TIME 86400

//??¢??°(00:00:00??????????§???°?????????)
int timeToNum(char* text) {
	int ans=0;
	//h
	ans += (text[0] - '0') * 60 * 60 * 10;
	ans += (text[1] - '0') * 60 * 60;
	//m
	ans += (text[3] - '0') * 60 * 10;
	ans += (text[4] - '0') * 60;
	//s
	ans += (text[6] - '0') * 10;
	ans += (text[7] - '0');

	return ans;
}

//?????????????????????
int imosu[DAY_TIME];

//??????????????¨??????
int N;

//??????????????¨??°?????????
char timeS[100];
char timeE[100];

//??????
int ans;

int main() {
	while (true) {
		//?????????
		memset(imosu,0,sizeof(int)*DAY_TIME);
		ans=0;

		//??\?????¨???????????¶
		cin>>N;
		if(N==0)break;

		for(int i=0;i<N;i++){
			//??\???
			cin >> timeS;
			cin >> timeE;
			
			//???????????????????????????
			imosu[timeToNum(timeS)]++;
			imosu[timeToNum(timeE)]--;
		}

		//????????????????????????????????????
		for (int i = 0; i < DAY_TIME-1; i++) {
			imosu[i+1]+=imosu[i];
			ans=max(ans,imosu[i+1]);
		}
		//?????§????????????
		cout<<ans<<endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define REP(i,n) for (int i = 1; i < (int)(n); i++)
template<class T> bool chmin(T &a, T b) {if(a>b) {a=b;return 1;}return 0;}
using namespace std;
using vint = vector<int>;
using vvint = vector<vector<int>>;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
using P = pair<int,int>;
const ll inf = 1e18;
const int mod = 1e5;
const int MAX = 1e6;

int main() {
    while (true) {
        int n; cin >> n;
        if (n == 0) break;
        vint c(24*60*60+2,0);
        rep(i,n) {
            string s, g; cin >> s >> g;
            int s_h = (s[0]-'0')*10+(s[1]-'0');
            int s_m = (s[3]-'0')*10+(s[4]-'0');
            int s_s = (s[6]-'0')*10+(s[7]-'0');
            int s_t = s_h*3600+s_m*60+s_s;
            int g_h = (g[0]-'0')*10+(g[1]-'0');
            int g_m = (g[3]-'0')*10+(g[4]-'0');
            int g_s = (g[6]-'0')*10+(g[7]-'0');
            int g_t = g_h*3600+g_m*60+g_s;
            c[s_t]++; c[g_t]--;
        }
        vint cover(24*60*60+1,0);
        rep(i,24*60*60+1) {
            if (i == 0) cover[i] = c[i];
            cover[i] = cover[i-1]+c[i];
        }
        int ans = 0;
        rep(i,24*60*60) ans = max(ans,cover[i]);
        cout << ans << endl;
    }
}

C++: #include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;

#define rep(i,N) for(int i=0;i<(int)(N);++i)
#define rrep(i,N) for(int i=(int)(N)-1;i>=0;--i)
#define debug(x) cout<<#x<<"="<<x<<endl;
constexpr ll MOD=1000000007;
constexpr ll INF=1LL<<60;
template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return true;}return false;}
template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return true;}return false;}
template<typename T> void fail(T v){cout << v << endl;exit(0);}
//template end

void solve(){
    int N;
    while((scanf("%d",&N),N)){
        vector<int> imos(101010);
        rep(i,N){
            int a,b,c;
            scanf("%d:%d:%d",&a,&b,&c);
            imos[a*3600+b*60+c]++;
            scanf("%d:%d:%d",&a,&b,&c);
            imos[a*3600+b*60+c]--;
        }
        rep(i,101001)imos[i+1]+=imos[i];
        printf("%d\n",*max_element(imos.begin(),imos.end()));
    }
}

int main(){
    //cin.tie(0);
    //ios::sync_with_stdio(false);
    //cout << fixed << setprecision(20);
    solve();
    return 0;
}