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 <vector>
#include <algorithm>
#include <set>
#include <queue>
#include <stack>
#include <string>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <sstream>

#define rep(i, n) for(int i = 0; i < n; i ++)
#define COUNT(i, n) for(int i = 1; i <= n; i ++)
#define ALL(T) T.begin(), T.end()
#define mp make_pair
#define pb push_back
#define ITER(c) __typeof((c).begin())
#define each(c, it) for(ITER(c) it = (c).begin(); it != (c).end(); it++)
#define X first
#define Y second
#define IN first
#define OUT second

using namespace std;

typedef pair<int, int> pii;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<string> vs;

const int INF = 1 << 24;

int main(void){
    for(int n, res; cin >> n, n; cout << res << endl){
        res = 0;
        vector<pii> t(n);
        rep(i, n){
            string out, in; cin >> out >> in;
            rep(j, 2) out.erase(out.find(":"), 1);
            rep(j, 2) in.erase(in.find(":") , 1);
            stringstream is;
            is << in;
            is >> t[i].IN;
            is.clear();
            is << out;
            is >> t[i].OUT;
        }
        sort(ALL(t));
        int wait = 0;
        priority_queue<int, vi, greater<int> > q;
        rep(i, n){
            while(!q.empty() && q.top() <= t[i].OUT)
                wait++, q.pop();

            if(!wait) res++;
            else wait--;
            
            q.push(t[i].IN);
        }
    }

    return 0;
}

C++: #include <iostream>
using namespace std;
 
int main() {
  while(1) {
    int n;
    cin >> n;
    if(n == 0) break;
 
    int limit = 24*3600;
    int data[limit];
    for(int i = 0; i < limit; i++) {
      data[i] = 0;
    }
 
    for(int i = 0; i < n; i++) {
      int h, m, s;
      int ss, gs;
      scanf("%d:%d:%d", &h, &m, &s);
      ss = h*3600 + m*60 +s;
      scanf("%d:%d:%d", &h, &m, &s);
      gs = h*3600 + m*60 +s;
      for(int j = ss; j < gs; j++) {
        data[j]++;
      }
    }
 
    int max = -1;
    for(int i = 0; i < limit; i++) {
      if(data[i] > max) max = data[i];
    }
 
    cout << max << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<iomanip>
#include<algorithm>
#include<bitset>
#include<cctype>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<functional>
#include<limits>
#include<list>
#include<map>
#include<set>
#include<stack>
#include<string>
#include<sstream>
#include<queue>
#include<vector>
using namespace std;
 
#define MOD 1000000007
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
 
int main() {
    int s[10000], g[10000], f[10000], hhs, mms, sss, hhg, mmg, ssg, cnt = 1;
    for(int n;cin>>n&&n;){
        
        
        for (int i = 0; i < n; i++) {
            char c;
            cin >> hhs >> c >> mms >> c >> sss >> hhg >> c >> mmg >> c >> ssg;
 
            s[i] = 3600 * hhs + 60 * mms + sss;
            g[i] = 3600 * hhg + 60 * mmg + ssg;
        }
		
		for(int i=0;i<n-1;i++)
			for(int j=n-1;j>i;j--)
				if(s[j-1]>s[j]){
					int tmp=s[j];
					s[j]=s[j-1];
					s[j-1]=tmp;
					tmp=g[j];
					g[j]=g[j-1];
					g[j-1]=tmp;
				}
		
		
		
        for (int i = 1; i < n; i++) {
            for (int j = 0; j < i;) {
                //cout << "j" << endl;
                if (f[j] == 1) { j++; continue; }
                if (s[i] >= g[j]) {
                    f[j] = 1;
                    break;
                }
                j++;
                if (j == i)cnt++;
            }
            //cout << "i" << endl;
        }
        //cout << "h" << endl;
        cout << cnt << endl;
        cnt = 1;
 
    }
    return 0;
}

C++: #include <cstdio>
#include <algorithm>
#include <vector>

using namespace std;

struct E {
    int time, c;
    E(int time, int c) : time(time), c(c) {}
    bool operator<(const E& e) const {
        return time < e.time;
    }
};

int N;
vector<E> es;
bool input() {
    es.clear();
    scanf("%d\n", &N);
    for (int i = 0; i < N; i++) {
        int h, m, s;
        scanf("%d:%d:%d", &h, &m, &s);
        int from = h * 3600 + m * 60 + s;
        es.push_back(E(from, +1));
        scanf(" %d:%d:%d\n", &h, &m, &s);
        int to = h * 3600 + m * 60 + s;
        es.push_back(E(to, -1));
    }
    return true;
}

void solve() {
    sort(es.begin(), es.end());
    int ans = 0;
    int pool = 0;
    for (int i = 0; i < es.size(); i++) {
        const E& e = es[i];
        if (e.c == 1) {
            if (pool > 0) pool--;
            else ans++;
        } else {
            pool++;
        }
    }
    printf("%d\n", ans);
}

int main() {
    while (input()) solve();
    return 0;
}

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

int	str_to_time(const string &time_str)
{
	int	hour, minute, second, time;
	hour = stoi(time_str.substr(0, 2));
	minute = stoi(time_str.substr(3, 2));
	second = stoi(time_str.substr(6, 2));
	time = hour * 3600 + minute * 60 + second;
	return time;
}

int	main()
{
	int	n;
	while (cin >> n) {
		if (n == 0) break;
		string	bgn, end;
		vector<int>	diff(24 * 3600, 0);
		for (int i = 0; i < n; ++i) {
			cin >> bgn >> end;
			diff.at(str_to_time(bgn)) += 1;
			diff.at(str_to_time(end)) -= 1;
		}
		vector<int>	cnt_vec(24 * 3600, 0);
		cnt_vec.at(0) = diff.at(0);
		for (int i = 1; i < 24 * 3600; ++i)
			cnt_vec.at(i) = cnt_vec.at(i - 1) + diff.at(i);
		cout << *max_element(cnt_vec.begin(), cnt_vec.end()) << endl;
	}
}