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 <string>
#include <vector>
using namespace std;

typedef long long ll;

ll f(string s){
    string s1,s2,s3;
    s1 = s.substr(0,2);
    s2 = s.substr(3,2);
    s3 = s.substr(6,2);

    int h = stoi(s1)*3600;
    int m = stoi(s2)*60;
    int ss = stoi(s3)*1;

    return h+m+ss;
}

void solve(int n){
    vector<int> v(60*60*60+3600+60+10,0);
    for(ll i=0;i<n;i++){
        string s1,s2;
        cin >> s1 >> s2;
        ll s=f(s1);
        ll t=f(s2);
        v[s]++;
        v[t]--;
    }
    for(int i=1;i<60*60*60+60*60+60;i++){
        v[i] = v[i] + v[i-1];
    }
    int ans = -1;
    for(int i=1;i<60*60*60+60*60+60;i++){
        ans = max(ans,v[i]);
        if(v[i] == 6)  cout << i << endl;
    }
    cout << ans << endl;
}

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

C++: #include<iostream>
#include<cstdio>
using namespace std;
int a[24 * 60 * 60+10];
int main() {
	long long a1, m1, a2, m2, a3, m3;
	int n;
	while (cin >> n&&n != 0) {
		int h1, m1, s1, h2, m2, s2;
		fill(a, a + 60 * 24 * 60+10, 0);
		int sum = 0;
		for (int i = 0; i<n; i++) {
			scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
			if (a[h1 * 3600 + m1 * 60 + s1] == 0) {
				sum++;
				for (int i = 0; i<24 * 60 * 60+10; i++) a[i]++;
			}
			for (int i = h1 * 3600 + m1 * 60 + s1; i<h2 * 3600 + m2 * 60 + s2; i++) {
				a[i]--;
			}
			a[h2 * 3600 + m2 * 60 + s2]++;
		}
		cout << sum << endl;
	}
}

C++: #include<cstdio>
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int main(){
    int n;
    while(scanf("%d",&n),n){
        int imoss[60*60*24+100]={0};
        for(int i=0;i<n;i++){
            int t,m,s;
            scanf("%d:%d:%d",&t,&m,&s);
            imoss[t*3600+m*60+s]++;
            scanf("%d:%d:%d",&t,&m,&s);
            imoss[t*3600+m*60+s]--;
        }
        int ma=0;
        for(int i=0;i<=24*60*60;i++)ma=max(ma,imoss[i]);
        printf("%d\n",ma);
    }
    return 0;
}

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

using namespace std;

struct Comparator {
  bool operator()(const pair<int, int>& l, const pair<int, int>& r) {
    if (l.first == r.first) {
      return l.second < r.second;
    } else {
      return l.first < r.first;
    }
  }
};

int main(int argc, char *argv[]) {
  while (true) {
    int n;
    cin >> n;
    if (n == 0) {
      break;
    }

    vector< pair<int, int> > table;
    for (int i = 0; i < n; i++) {
      int h, m, s;
      int hatsu, tyaku;
      scanf("%d:%d:%d", &h, &m, &s);
      hatsu = (h * 60 + m ) * 60 + s;
      scanf("%d:%d:%d", &h, &m, &s);
      tyaku = (h * 60 + m ) * 60 + s;
      table.push_back(pair<int, int>(hatsu, tyaku));
    }

    for (int i = 0; i < n; i++) {
      cout << table[i].first << " -> " << table[i].second << endl;
    }

    struct Comparator comparator;
    sort(table.begin(), table.end(), comparator);
    vector<int> train;
    bool avail = false;
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < train.size(); j++) {
        if (train[j] <= table[i].first) {
          avail = true;
          train[j] = table[i].second;
          break;
        }
      }
      if (avail) {
        avail = false;
        continue;
      }
      train.push_back(table[i].second);
    }

    cout << train.size() << endl;
    train.clear();
  }
  return 0;
}

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

int main(){
	int n;
	int m[86400]={};
	while(cin >> n,n){
		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;
	}
}