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>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<29;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-11;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int g(string s){
	return atoi(s.c_str());
}

int f(string t){
	int h=g(t.substr(0,2));
	int m=g(t.substr(3,2));
	int s=g(t.substr(6,2));
	return h*60*60+m*60+s;
}

const int M=100000;

int main(){
	while(1){
		int n;
		cin>>n;
		if(n==0) break;
		vi a(M);
		for(int i=0;i<n;i++){
			string s,t;
			cin>>s>>t;
			a[f(s)]++;
			a[f(t)]--;
		}
		for(int i=1;i<M;i++) a[i]+=a[i-1];
		int res=0;
		for(auto i:a) res=max(res,i);
		cout<<res<<endl;
	}
}

C++: #include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <algorithm>
#include <functional>
#include <utility>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstdio>

#define rep(i, n) for(int (i) = 0; (i) < (n); (i)++)

class Solve {
public:
	Solve() {};
	~Solve() {};

	void solver() {
		std::vector<int> results;
		while (1) {
			int n;
			std::cin >> n;
			if (!n) break;

			std::vector<std::pair<int, int>> times;
			std::string str;
			rep(i, n) {
				times.push_back(std::make_pair(0, 0));
				std::cin >> str;
				times.back().first = std::stoi(str.substr(6, 2)) + std::stoi(str.substr(3, 2)) * 60 + std::stoi(str.substr(0, 2)) * 3600;
				std::cin >> str;
				times.back().second = std::stoi(str.substr(6, 2)) + std::stoi(str.substr(3, 2)) * 60 + std::stoi(str.substr(0, 2)) * 3600;
			}
			std::sort(times.begin(), times.end(), std::greater<std::pair<int, int>>());
			//???????????????????????????
			std::vector<int> usingTrain; //int?????°?????????
			int maxTrain = 0;
			while (!times.empty()) {
				int leave = times.back().first;
				int arrive = times.back().second; times.pop_back();
				//??°???????????????????????????
				std::sort(usingTrain.begin(), usingTrain.end(), std::greater<int>());
				//????????°???
				if (!usingTrain.empty()) {
					//????????°?????????????????????????????°???
					if (leave >= usingTrain.back()) {
						usingTrain.pop_back();
					}
				}
				//??????
				usingTrain.push_back(arrive);
				if (maxTrain < usingTrain.size()) maxTrain = usingTrain.size();
			}
			results.push_back(maxTrain);
		}
		for (auto& x : results) {
			std::cout << x << std::endl;
		}
	}
private:
};

int main() {
	Solve solve;
	solve.solver();
	getchar(); getchar();
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define REP(i,n) for(int i=0; i < (n); ++i)
#define REPR(i,n) for(int i=(n); i >= 0; --i)
#define FOR(i, m, n) for(int i = (m); i < (n); ++i)
#define INF 1e9
// constexpr ll INF = 1LL << 60;

void solve(int n){
  int w = 86400;
  vector<int> sum(w+1, 0);
  REP(i, n){
    string s, e;
    cin >> s >> e;
    int st = 0, et = 0;
    st += stoi(s.substr(0, 2))*3600+ stoi(s.substr(3,2))*60 + stoi(s.substr(6, 2));
    et += stoi(e.substr(0, 2))*3600+ stoi(e.substr(3,2))*60 + stoi(e.substr(6, 2));
    sum[st]++, sum[et]--;
  }
  int ans = sum[0];
  REP(i, w){
    sum[i+1] += sum[i];
    ans = max(ans, sum[i+1]);
  }
  cout << ans << endl;
}

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

C++: #include <iostream>
#include <string>
#include <array>
#include <vector>
#include <math.h>
#include <algorithm>
#include <set>
#include <deque>
#include <utility>
#include <map>

using namespace std;

int main(void)
{
	vector <string> s, t; //s????????????t?????°???
	multimap<int, int> mp;
	vector <pair<int, int>> pr;
	vector <int> ans;
	string temp1, temp2;
	int m, n;
	int temp;
	int i, j, k;
	int count = 0; //???????????¬??°
	int max = 0;

	while (1) {

		cin >> n;
		if (n == 0) {
			break;
		}

		for (i = 0; i < n; i++) {
			cin >> temp1 >> temp2;


			temp = stoi(temp1.substr(0, 2)) * 3600 + stoi(temp1.substr(3, 2)) * 60 + stoi(temp1.substr(6, 2));

			pr.push_back(make_pair(temp, 1));

			temp = stoi(temp2.substr(0, 2)) * 3600 + stoi(temp2.substr(3, 2)) * 60 + stoi(temp2.substr(6, 2));

			pr.push_back(make_pair(temp, 0));


		}
		sort(pr.begin(), pr.end());

		for (i = 0; i < pr.size(); i++) {
			
			if (pr[i].second == 1) {
				count++;
				if (max < count) {
					max = count;
				}

			}
			else if (pr[i].second == 0) {
				count--;
			}

	
			

		}

		pr.clear();

		ans.push_back(max);
		max = 0;

	}

	for (i = 0; i < ans.size(); i++) {
		cout << ans[i] << endl;
	}



	return (0);
}