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 <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
#define INF 999999999
using namespace std;
typedef pair<int, int> P;
typedef pair<llong, llong> LP;
typedef pair<int, P> PP;
typedef pair<llong, LP> LPP;

//int dy[]={0, 0, 1, -1, 0};
//int dx[]={1, -1, 0, 0, 0};

bool solve(){
	int n;
	scanf("%d", &n);
	if(n==0) return 0;
	
	vector<int> sh(n), sm(n), ss(n);
	vector<int> rh(n), rm(n), rs(n);
	vector<vector<vector<int> > > imos(30, vector<vector<int> >(65, vector<int>(65, 0)));
	REP(i, n){
		scanf("%d:%d:%d %d:%d:%d", &sh[i], &sm[i], &ss[i], &rh[i], &rm[i], &rs[i]);
		imos[sh[i]][sm[i]][ss[i]]+=1;
		imos[rh[i]][rm[i]][rs[i]]-=1;
	}
	
	REP(i, 24){
		REP(j, 60){
			REP(k, 60){
				if(i+j+k==0) continue;
				
				if(k>0) imos[i][j][k]+=imos[i][j][k-1];
				else if(j>0) imos[i][j][k]+=imos[i][j-1][59];
				else imos[i][j][k]+=imos[i-1][59][59];
			}
		}
	}
	
	int maxi=-1;
	REP(i, 24){
		REP(j, 60){
			REP(k, 60){
				//cout << imos[i][j][k] << endl;
				maxi=max(maxi, imos[i][j][k]);
			}
		}
	}
	
	printf("%d\n", maxi);
	return 1;
}

int main(){
	while(solve()){}
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)

void slove(int n){
	vector<int> v(86400);
	rep(i, 86400) v[i] = 0;//?????????
	rep(i, n){
		string s, e;
		cin >> s >> e;
		//?§???°?????????
		int start = 36000 * (s[0] - '0') + 3600 * (s[1] - '0') 
					+ 600 * (s[3] - '0') + 60 * (s[4] - '0')
					+ 10 * (s[6] - '0') + 1 * (s[7] - '0');
		int end = 36000 * (e[0] - '0') + 3600 * (e[1] - '0') 
					+ 600 * (e[3] - '0') + 60 * (e[4] - '0')
					+ 10 * (e[6] - '0') + 1 * (e[7] - '0');
		//printf("%d %d\n", start, end);
		for (int j = start; j < end ; ++j) v[j]++;//???????????????
	}
	int ans = 0;

	
	rep(i, 86400){
		ans = max(ans, v[i]);
	}
	
	//sort(all(v));
	//reverse(all(v));
	printf("%d\n", ans);
	return;
}
int main(void){
	rep(i, 100000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <algorithm>
#include <map>
#include <vector>
using namespace std;
vector<pair<int,int> > v[2];
int main(void){
  int res;
  int n,f;
  while(cin >> n && n){
    f = res = 0;
    v[0].clear();
    for(int i = 0; i < n; i++){
      int a,b,c,d;
      scanf("%d:%d:%d",&a,&b,&c);
      d = a*3600 + b*60 + c;
      scanf("%d:%d:%d",&a,&b,&c);
      c = a*3600 + b*60 + c;
      v[0].push_back(make_pair(d,c));
    }

    sort(v[0].begin(),v[0].end());

    while((int)v[f].size()){
      res++;
      int b = v[f][0].second;
      v[(f+1)%2].clear();
      for(int i = 1; i < (int)v[f].size(); i++){
	if(v[f][i].first < b){
	  v[(f+1)%2].push_back(v[f][i]);
	}
      }
      f = (f+1)%2;
    }
    cout << res << endl;
  }
}

C++: #include <vector>
#include <cstdio>
#include <algorithm>
using namespace std;
main(){
	int N,i,h,m,d;
	for(;scanf("%d",&N),N;printf("%d\n",m)){
		vector<pair<int,int> >v;
		for(i=0;i<N*2;i++)scanf("%d:%d:%d",&h,&m,&d),v.push_back(make_pair(h*3600+m*60+d,i%2?-1:1));
		sort(v.begin(),v.end());
		for(h=m=i=0;i<N*2;i++)h+=v[i].second,m=max(m,h);
	}
}

C++: #include <sstream>
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <iostream>
#include <utility>
#include <set>
#include <cctype>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
using namespace std;
#define INF 100000000

typedef long long ll;
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};

int table[100000];

int main(void) {
    int n;
    while (cin >> n) {
        if (n == 0) break;
        for (int i = 0; i < n; i++) {
            string s, t;
            cin >> s >> t;
            // 最初の時間を求める
            {
                int h = (s[0]-'0') * 10 + (s[1]-'0');
                int m = (s[3]-'0') * 10 + (s[4]-'0');
                int ss = (s[6]-'0') * 10 + (s[7]-'0');
                table[h*3600+m*60+ss]++;
            }
            // 到着の時間を求める
            {
                int h = (t[0]-'0') * 10 + (t[1]-'0');
                int m = (t[3]-'0') * 10 + (t[4]-'0');
                int ss = (t[6]-'0') * 10 + (t[7]-'0');
                table[h*3600+m*60+ss]--;
            }
        }
        int cur = 0, ans = 0;
        for (int i = 0; i < 100000; i++) {
            cur += table[i];
            ans = max(ans, cur);
        }
        cout << ans << endl;
    }
    return 0;
}