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>

using namespace std;

int main() {
    int n, h, m, s, start, stop;
    while (true) {
        cin >> n;
        int table[60*60*24] = {};
        if (n == 0) {
            break;
        }
        for (int i=0; i<n; i++) {
            scanf("%d:%d:%d", &h, &m, &s);
            start = 3600*h+60*m+s;
            scanf("%d:%d:%d", &h, &m, &s);
            stop = 3600*h+60*m+s;
            for (int t=start; t<stop; t++) {
                table[t]++;
            }
        }
        int most_trains = 0;
        for (int t=0; t<60*60*24; t++) {
            if (table[t] > most_trains) {
                most_trains = table[t];
            }
        }
        cout << most_trains << endl;
    }
    return 0;
}

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

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

using namespace std;

#define MAX (23*60*60+59*60+59+1)
int arr[MAX];

int main() {
  int n;
  while( cin >> n, n ) {
    memset(arr,0,sizeof arr);
    int h,m,s;
    rep(i,n) {
      scanf("%d:%d:%d",&h,&m,&s);
      arr[h*60*60+m*60+s] += 1;
      scanf("%d:%d:%d",&h,&m,&s);
      arr[h*60*60+m*60+s] += -1;
    }
    int maxi = arr[0];
    REP(i,1,MAX) {
      arr[i] += arr[i-1];
      maxi = max(maxi,arr[i]);
    }
    cout << maxi << endl;
  }
  return 0;
}

C++: #include <vector>
#include <cstdio>
using namespace std;

int main(){
    vector< vector<int> > trains;
    int n,i,j,k,f,t,h,m,s,flg;
    while(1){
        scanf("%d",&n);
        if(!n){break;}
        for(i=0;i<n;i++){
            scanf("%d:%d:%d",&h,&m,&s);
            f=h*3600+m*60+s;
            scanf("%d:%d:%d",&h,&m,&s);
            t=h*3600+m*60+s;
            if(trains.empty()){
                vector<int> buf(86401,0);
                for(j=f;j<=t;j++){buf[i]=1;}
                trains.push_back(buf);
            }
            else{
                for(auto itr=trains.begin();itr!=trains.end();itr++){
                    flg=0;
                    for(j=f+1;j<t;j++){if((*itr)[j]){flg=1;break;}} 
                    if(!flg){
                        for(j=f;j<=t;j++){(*itr)[j]=1;}
                        break;
                    }
                }
                if(flg){
                    vector<int> buf(86401,0);
                    for(j=f;j<=t;j++){buf[j]=1;}
                    trains.push_back(buf);
                }
            }
        }
        printf("%lu\n",trains.size());
    }
    return 0;
}

C++: #include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

int n;
int dif[90000], sum[90000];
int S[10005], T[10005];

int gettime()
{
  string tmp;
  char c; int ret = 0;

  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 3600;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str()) * 60;
  cin >> c;

  tmp.clear();
  cin >> c, tmp += c;
  cin >> c, tmp += c;
  ret += atoi(tmp.c_str());

  return ret;
}

int main(void)
{
  while(1){
    cin >> n;
    if(n == 0) break;

    for(int i = 0; i <= 86405; i++) dif[i] = 0;

    for(int i = 0; i < n; i++){
      S[i] = gettime();
      T[i] = gettime();
    }

    /*for(int i = 0; i < n; i++){
      cout << S[i] << " " << T[i] << endl;;
    }*/

    for(int i = 0; i < n; i++){
      dif[S[i]]++;
      dif[T[i]]--;
    }
    sum[0] = dif[0];
    for(int i = 1; i <= 86405; i++){
      sum[i] = sum[i-1] + dif[i];
    }

    int ans = 0;
    for(int i = 0; i <= 86405; i++){
      if(sum[i] == 6) cout << i << endl;
      ans = max(ans, sum[i]);
    }
    cout << ans << endl;
  }

  return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<cstdio>
#include<climits>
#include<cmath>
#include<cstring>
#include<string>
#include<sstream>
#include<numeric>
#include<cassert>

#define f first
#define s second
#define mp make_pair

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define rep(i,s,n) for(int i=(s); i<(int)(n); i++)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); i++)
#define ALL(c) (c).begin(), (c).end()
#define IN(x,s,g) ((x) >= (s) && (x) < (g))
#define ISIN(x,y,w,h) (IN((x),0,(w)) && IN((y),0,(h)))
#define print(x) printf("%d\n",x)

using namespace std;

typedef unsigned int uint;
typedef long long ll;

const int _dx[] = {0,1,0,-1};
const int _dy[] = {-1,0,1,0};

int getInt(){
  int ret = 0,c;
  c = getchar();
  while(!isdigit(c)) c = getchar();
  while(isdigit(c)){
    ret *= 10;
    ret += c - '0';
    c = getchar();
  }
  return ret;
}

int cnt[60*60*24 + 1];

int main(){
  int n;
  while(scanf("%d",&n), n){
    int h,m,s,hh,mm,ss;
    memset(cnt, 0, sizeof(cnt));
    REP(i,n){
      scanf("%d:%d:%d %d:%d:%d",&h,&m,&s,&hh,&mm,&ss);
      //printf("%d:%d:%d %d:%d:%d\n",h,m,s,hh,mm,ss);
      int st = h * 3600 + m * 60 + s;
      int ed = hh* 3600 + mm* 60 + ss;

      do{
        ++cnt[st];
      }while(++st < ed);
    }

    int ans = 0;
    REP(i,60*60*24+1)
      ans = max(ans, cnt[i]);

    print(ans);
  }
  return 0;
}