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 <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>
#include <functional>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

struct UnionFind {
	vector<int> v;
	UnionFind(int n) : v(n)  { for (int i = 0; i < n; i++) v[i] = i; }
	int  find(int x)         { return v[x] == x ? x : v[x] = find(v[x]); }
	void unite(int x, int y) { v[find(x)] = find(y); }
};

int main() {
	int n;
	while (cin >> n, n) {
		vector<pair<int, bool>> jikoku;
		REP(i, n) {
			string s;
			cin >> s;
			jikoku.push_back({ (s[0]-'0')*36000+ (s[1] - '0') * 3600 + (s[3] - '0') * 600 + (s[4] - '0') * 60 + (s[6] - '0') * 10 + (s[7] - '0') * 1,true });
			cin >> s;
			jikoku.push_back({ (s[0] - '0') * 36000 + (s[1] - '0') * 3600 + (s[3] - '0') * 600 + (s[4] - '0') * 60 + (s[6] - '0') * 10 + (s[7] - '0') * 1,false });
		}
		SORT(jikoku);
		int cnt = 0;
		int ans = 0;
		REP(i, n * 2) {
			if (jikoku[i].second) {
				cnt++;
			}
			else {
				cnt--;
			}
			ans = max(ans, cnt);
		}
		cout << ans << endl;
	}

}

C++: #include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
 
using namespace std;
 
#define rep(i,n) for(int i=0; i<(n); i++)
#define repc(i,s,e) for(int i=(s); i<(e); i++)
#define pb(n) push_back((n))
#define mp(n,m) make_pair((n),(m))
#define all(r) r.begin(),r.end()
#define fi first
#define se second
 
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<ll> vl;
typedef vector<vl> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
 
 
const int INF = 10000000;

int tos(int h, int m, int s){
	return h * 3600 + m * 60 + s;
}

bool cmp(pii p1, pii p2){
	if(p1.se != p2.se) return p1.se < p2.se;
	return p1.fi < p2.fi;
}

int main(){
	int n;
	int h, m, s;
	pii p;
	while(cin>>n && n > 0){
		vector<pii> v;
		for(int i = 0; i < n; i++){
			scanf("%d:%d:%d", &h, &m, &s);
			p.se = tos(h, m, s);
			scanf("%d:%d:%d", &h, &m, &s);
			p.fi = tos(h, m, s);
			v.pb(p);
		}
		sort(all(v), cmp);
		vi u;
		u.pb(v[0].fi);
		for(int i = 1; i < v.size(); i++){
			for(int j = 0; j < u.size(); j++){
				if(u[j] <= v[i].se){
					u[j] = v[i].fi;
					break;
				}
				if(j == u.size() - 1) {
					u.pb(v[i].fi);
					break;
				}
			}
			sort(all(u));
		}
		cout<<u.size()<<endl;
	}
}

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

using namespace std;

int main(void) {
    int n;
    while (cin >> n, n) {
        int T[86410] = {};
        for (int i = 0; i < n; i++) {
            int h[2], m[2], s[2], t[2];
            for (int j = 0; j < 2; j++) {
                scanf("%d:%d:%d", &h[j], &m[j], &s[j]);
                t[j] = h[j] *3600 + m[j]*  60 + s[j];
                if (!j) T[t[j]]++;
                else T[t[j]]--;
            }
        }

        int ans = 0;
        for (int i = 0; i < 86400; i++) {
            if (i) T[i] += T[i - 1];
            ans = max(ans, T[i]);
        }
        
        cout << ans << endl;
    }

    return 0;
}

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

typedef pair< int, int > iP;

int main() {

    int n;

    while(cin >> n, n) {
        vector< iP > v;
        vector< int > t(24 * 3600, 0);
        for(int i = 0; i < n; i++) {
            int h, m, s, hh, mm, ss;
            scanf("%2d:%2d:%2d %2d:%2d:%2d", &h, &m, &s, &hh, &mm, &ss);
            v.push_back(iP(h * 3600 + m * 60 + s, hh * 3600 + mm * 60 + ss));
            t[v[v.size() - 1].first]++, t[v[v.size() - 1].second]--;
        }

        int sum = 0, wait = 0, ans = 0;
        for(int i = 0; i < 24 * 3600; i++) {
            if(t[i] > 0) {
                if(wait <= 0) {
                    ans++;
                    sum++;
                } else {
                    wait--;
                }
            } else if(t[i] < 0 && wait < sum) {
                wait++;
            }
        }
        cout << ans << endl;
    }
}