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 <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

int main(){
  int n;
  int h1,h2,m1,m2,s1,s2;
  int dp[3600*60+1];
  while(cin >> n, n){
    memset(dp, 0, sizeof(dp));
    for(int i = 0 ; i < n ; i++){
      scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
      int t1 = h1*3600+m1*60+s1, t2 = h2*3600+m2*60+s2;
      dp[t1]++, dp[t2]--;
    }
    int ans = 0;
    for(int i = 1 ; i <= 3600*60 ; i++){
      dp[i] = dp[i-1]+dp[i];
      ans = max(ans, dp[i]);
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;
static const int N = 10000;
int Change(string);
struct data{
  int sh,sm,ss,eh,em,es;
  bool operator<(const data& right)const{
    if(eh!=right.eh) return eh<right.eh;
    if(em!=right.em) return em<right.em;
    if(es!=right.es) return es<right.es;
    if(sh!=right.sh) return sh<right.sh;
    if(sm!=right.sm) return sm<right.sm;
    return ss<right.ss;
  }
};
int main(){
  int n,cnt,check[N],ok,flag,Max,i,j;
  int comh,comm,coms;
  string start[N],end[N],sub;
  while(1){
    cin >> n;
    vector<data> V(n);
    cnt=0;
    if(n==0) break;
    for(i=0;i<n;i++){
      cin >> start[i] >> end[i];
      check[i]=-1;
      sub=start[i].substr(0,2);
      V[i].sh=Change(sub);
      sub=start[i].substr(3,2);
      V[i].sm=Change(sub);
      sub=start[i].substr(6,2);
      V[i].ss=Change(sub);
      sub=end[i].substr(0,2);
      V[i].eh=Change(sub);
      sub=end[i].substr(3,2);
      V[i].em=Change(sub);
      sub=end[i].substr(6,2);
      V[i].es=Change(sub);
    }
    sort(V.begin(),V.end());
    for(i=0;i<n;i++){
      if(check[i]==-1){
	check[i]=i;
	comh=V[i].eh;
	comm=V[i].em;
	coms=V[i].es;
	for(j=i+1;j<n;j++){
	  if(check[j]==-1){
	    ok=0;
	    if(comh==V[j].sh){
	      if(comm==V[j].sm){
		if(coms<=V[j].ss) ok=1;
	      }
	      else if(comm<V[j].sm) ok=1;
	    }
	    else if(comh<V[j].sh) ok=1;
	    if(ok==1){
	      check[j]=i;
	      comh=V[j].eh;
	      comm=V[j].em;
	      coms=V[j].es;
	    }
	  }
	}
      }
    }
    Max=0;
    for(i=0;i<n;i++){
      Max=max(Max,check[i]);
    }
    cout << Max+1 << endl;
  }
  return 0;
}
int Change(string sub){
  int ret=0,x=1,i;
  for(i=0;i<2;i++){
    ret=ret*x+(sub[i]-'0');
    x=10;
  }
  return ret;
}

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

static const int MAX = 3600*24+60*60+60;

int main(){
    while(1){
        int N;
        cin>>N;
        if(N == 0) break;
        vector<int> V(MAX,0);

        for(int i=0; i<N; i++){
            int h1,h2,m1,m2,s1,s2;
            scanf("%d:%d:%d",&h1,&m1,&s1);
            scanf("%d:%d:%d",&h2,&m2,&s2);
            int left = 3600*h1+60*m1+s1;
            int right = 3600*h2+60*m2+s2;
            V[left]++;
            V[right]--;
        }

        int ans = 0;

        for(int i=0; i<MAX; i++){
            V[i+1] += V[i];
            ans = max(ans,V[i+1]);
        }

        cout<<ans<<endl;
    }

    return 0;
}

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

int n;
std::string dep, arr;

int main() {
    while (true) {
        std::cin >> n;
        if (n == 0) {
            return 0;
        }
        std::vector<int> vec(86401, 0);
        for (int i = 0; i < n; i++) {
            std::cin >> dep >> arr;
            int dep_time = std::stoi(dep.substr(0, 2))*3600+std::stoi(dep.substr(3, 2))*60+std::stoi(dep.substr(6,2));
            int arr_time = std::stoi(arr.substr(0, 2))*3600+std::stoi(arr.substr(3, 2))*60+std::stoi(arr.substr(6,2));
            vec[dep_time]++;
            vec[arr_time]--;
        }
        for (int i = 1; i < 86400; i++) {
            vec[i] += vec[i-1];
        }
        std::cout << *std::max_element(vec.begin(), vec.end()) << std::endl;
    }
}

C++: #include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
#include <cstring>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define CLR(mat) memset(mat, 0, sizeof(mat))
typedef long long ll;
const int MAX = 24 * 60 * 60 + 100;
int f(int h, int m, int s) {
  return h * 3600 + m * 60 + s;
}
int main()
{
  int n;
  int imos[MAX];
  while(cin>>n,n) {
    int ans = 0;
    CLR(imos);
    FOR(i,0,n) {
      int h1, m1, s1;
      int h2, m2, s2;
      scanf("%d:%d:%d %d:%d:%d",&h1,&m1,&s1,&h2,&m2,&s2);
      imos[f(h1,m1,s1)]++;
      imos[f(h2,m2,s2)]--;
    }
    FOR(i,0,MAX-1) {
      imos[i+1] += imos[i];
      ans = max(ans, imos[i+1]);
    }
    cout << ans << endl;
  }
  return 0;
}