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<cstdlib>
using namespace std;

int Hen(char s,char t){
  return ((s-'0')*10+(t-'0'));
}
int main()
{
  string s,f;
  int n,a,b,max,T[86401]={};
  while(1){
    cin>>n;
    if(n==0)break;
    for(int i=0;i<n;i++){
      cin>>s>>f;
      a=(Hen(s[0],s[1])*3600+Hen(s[3],s[4])*60+Hen(s[6],s[7]));
      b=(Hen(f[0],f[1])*3600+Hen(f[3],f[4])*60+Hen(f[6],f[7]));
      for(int j=a;j<b;j++)T[j]++;
    }
    max=0;
    for(int i=0;i<86401;i++){
      if(max<T[i])max=T[i];
      T[i]=0;
    }
    cout<<max<<endl;
  }
  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>> stime, ttime;
	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));

			mp.insert(make_pair(temp, 0));

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

			mp.insert(make_pair(temp, 1));


		}
		auto itr = mp.begin();

		for (i = 0; i < mp.size(); i++) {

			if (itr->second == 0) {
				count++;
				if (max < count) {
					max = count;
				}

			}
			else if (itr->second == 1) {
				count--;
			}

	
			itr++;

		}

		mp.clear();

		ans.push_back(max);

	}

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



	return (0);
}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <queue>
#include <algorithm>
#define INF 1 << 28
using namespace std;

typedef pair<int,int> P;

int main ()
{
    int n;
    while (cin >> n, n) {
        string str1, str2;
        vector<P> time;
        while (n--) {
            cin >> str1 >> str2;
            for (int i = 0; i < str1.size(); i++) {
                if (str1[i] == ' ') {
                    str1[i] = str2[i] = ' ';
                }
            }

            stringstream ss1, ss2;
            ss1 << str1;
            ss2 << str2;

            int t1, t2, t3;
            ss1 >> t1 >> t2 >> t3;
            int s = t1 * 60 * 60 + t2 * 60 + t3;
            ss2 >> t1 >> t2 >> t3;
            int e = t1 * 60 * 60 + t2 * 60 + t3;

            time.push_back(P(s,1));
            time.push_back(P(e,-1));
        }

        sort(time.begin(), time.end());

        int res = 0, MAX = 0;
        for (int i = 0; i < time.size(); i++) {
            res += time[i].second;
            MAX = max(MAX, res);
        }

        cout << MAX << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#include <stdint.h>

typedef uint32_t u32;
typedef uint64_t u64;
typedef std::pair<int, int> pii;

int t1[20000];
int t2[20000];
bool used[20000];
int n;

void solve(int id, int t) {
  for(int i = id; i < n; ++i) {
    if( used[i] ) continue;
    if( t <= t1[i] ) {
      used[i] = true;
      solve(i + 1, t2[i]);
      return;
    }
  }
  return;
}
  
int main() {

  for(;;) {
    int h1, m1, s1, h2, m2, s2;
    scanf("%d", &n);
    if( n == 0 ) break;
    for(int i = 0; i < n; ++i) {
      scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
      t1[i] = h1 * 3600 + m1 * 60 + s1;
      t2[i] = h2 * 3600 + m2 * 60 + s2;
    }
    for(int i = 0; i < n; ++i) used[i] = false;
    int res = 0;
    for(int i = 0; i < n; ++i) {
      if( not used[i] ) {
        solve(i, 0);
        res += 1;
      }
    }
    std::cout << res << std::endl;
  }      

  return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int main() {
	int n;
	while (cin >> n, n) {
		int imos[86410] = {};
		for (int i = 0; i < n; i++) {
			int a, b, c, d, e, f;
			scanf("%d:%d:%d", a, b, c);
			scanf("%d:%d:%d", d, e, f);
			imos[a * 3600 + b * 60 + c]++;
			imos[d * 3600 + e * 60 + f]--;
		}
		int ans = imos[0];
		for (int i = 1; i <= 86400; i++) {
			imos[i] += imos[i - 1];
			ans = max(ans, imos[i]);
		}
		cout << ans << endl;
	}
}