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;
typedef long long ll;
typedef long double ld;
typedef pair< ll, ll > Pi;
#define rep(i,n) for(ll i=0;i<(n);i++)
#define rep2(i,n) for(ll i=1;i<=(n);i++)
#define rep3(i,i0,n) for(ll i=i0;i<(n);i++)
#define pb push_back
#define MOD 1000000007
const ll INF = 1LL << 60;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
ll gcd(ll a, ll b) {return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) {return a/gcd(a,b)*b;}
#define all(x) x.begin(), x.end()
#define mp make_pair
bool compare(Pi a, Pi b) {
    if(a.first != b.first){
        return a.first < b.first;
        
    }else{
        return a.second < b.second;
    }
}

bool comparex(tuple<ll,ll,ll> a, tuple<ll,ll,ll> b) {

    return get<1>(a) < get<1>(b);
        
}
bool comparey(tuple<ll,ll,ll> a, tuple<ll,ll,ll> b) {

    return get<2>(a) < get<2>(b);
        
}


bool In_map(ll y,ll x,ll h,ll w){
    if(y<0 || x<0 || y>=h || x>=w){
        return 0;
    }else{
        return 1;
    }
}
const vector<ll> dx{1,0,-1,0};
const vector<ll> dy{0,1,0,-1};

#define mod 100000
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res+=a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res-=a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res*=a;
  }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }
 
  // for prime mod
  mint inv() const {
    return pow(mod-2);
  }
  mint& operator/=(const mint a) {
    return (*this) *= a.inv();
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res/=a;
  }
};




int main() {
    while(1){
    ll n;
    cin>>n;
    if(n == 0) break;
    vector<ll> str(25*3600);
    vector<ll> end(25*3600);

    rep(i,n){
        ll h,m,s;
        char c;
        cin >>h>>c>>m>>c>>s;
        str[h*3600+m*60+s]++;
        cin >>h>>c>>m>>c>>s;
        end[h*3600+m*60+s]++;
        //cout <<h<<" "<<m<<" "<<s<<endl;
    }
    ll now = 0;
    ll mx = 0;
    rep(i,25*3600){
        now = now + str[i]-end[i];
        chmax(mx,now);
    }
    cout<<mx<<endl;
    }

    return 0;
    

}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <utility>
#include <cstring>
#include <iomanip>
#include <numeric>
#include <cmath>
#include <cassert>
#include <complex>
#include <deque>
#define repi(i,x,n) for(int i = x; i < n; i++)
#define rep(i,n) repi(i,0,n)
#define int long long
using namespace std;
const int INF = 1<<30;
const int MOD = 1e9 + 7;
const double EPS = 1e-8;
int n;
signed main(void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    int time;
    deque<pair<int,int> > ans;
    while(1){
        cin>>n;
        if(n==0) break;
        rep(i,n*2){
            string s;
            cin>>s;
            time=0;
            int check= 1;
            if(i%2==1) check=-1;
            time+=stoi(s.substr(0,2)) * 10000;
            time+=stoi(s.substr(3,2)) * 100;
            time+=stoi(s.substr(6));
            ans.push_back(make_pair(time,check) );
        }
        sort(ans.begin(),ans.end() );
        int cnt=0;
        int num=0;
        rep(i,n*2){
            cnt+=ans[0].second;
            ans.pop_front();
            num=max(num,cnt);
        }
        cout<<num<<endl;
    }
            
    return 0;
}

C++: #include<iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;

int main(){
	int n;
	while(cin >> n,n){
		int m[86400]={};
		for(int i=0;i<n;i++){
			int bh,bm,bs,eh,em,es;
			scanf("%d:%d:%d %d:%d:%d",&bh,&bm,&bs,&eh,&em,&es);
			m[(bh*60*60)+(bm*60)+bs]+=1;
			m[(eh*60*60)+(em*60)+es]+=-1;
		}
		int count=0,ans=0;
		for(int i=0;i<86400;i++){
			count+=m[i];
			ans=max(ans,count);
		}
		cout << ans << endl;
	}
}

C++: #include<iostream>
#include<string>
#include<queue>
using namespace std;
int main(){
  while(1){
    int n;
    string a[10001],b;
    priority_queue<string,vector<string>,greater<string> > c;
    cin>>n;
    if(n==0)break;
    for(int i=0;i<n;i++){
      cin>>a[i]>>b;
      c.push(b);
    }
    int cnt=0;
    for(int i=0;i<n;i++){
      if(a[i]>=c.top()){
	c.pop();
      }else cnt++;
    }
    cout<<cnt<<endl;
  }
  return 0;
}

C++: #include "bits/stdc++.h"

using namespace std;

long long int N,M,K,L,R,H,W;

const long long int MOD=1000000007;



int main(){
	
	while(cin>>N,N){
		vector<int>v(86401);
		for(int i=0;i<N;i++){
			string s,t;
			cin>>s>>t;
			int a=((s[0]-'0')*10+(s[1]-'0'))*3600+((s[3]-'0')*10+s[4]-'0')*60+((s[6]-'0')*10+s[7]-'0');
			int b=((t[0]-'0')*10+(t[1]-'0'))*3600+((t[3]-'0')*10+t[4]-'0')*60+((t[6]-'0')*10+t[7]-'0');
			v[a]++;
			v[b]--;
		}
		for(int i=1;i<=86400;i++)v[i]+=v[i-1];
		cout<<*max_element(v.begin(),v.end())<<endl;
	}
	return 0;
}