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>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

const ll DT = 24 * 60 * 60 + 1;

ll f(const string &str) {
    ll h = atoi(str.substr(0, 2).c_str());
    ll m = atoi(str.substr(3, 2).c_str());
    ll s = atoi(str.substr(6, 2).c_str());
    return h * 60 * 60 + m * 60 + s;
}

void solve(ll n) {
    vector<string> st(n), en(n);
    rep(i, n) cin >> st[i] >> en[i];
    vector<ll> dp(DT + 1, 0);
    rep(i, n) {
        dp[f(st[i])]++;
        dp[f(en[i])]--;
    }
    ll ans = dp[0];
    rep(i, DT) {
        dp[i + 1] += dp[i];
        ans = max(ans, dp[i + 1]);
    }
    cout << ans << endl;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    while(true) {
        ll n;
        cin >> n;
        if (n == 0) break;
        solve(n);
    }
    return 0;
}

C++: #include <bits/stdc++.h>
#define ADAY 86400
using namespace std;
typedef long long ll;

int main(void){
  ll n;
  while(cin >> n, n){
    vector < pair < ll, ll > > t;
    for(ll i=0; i < n; i++){
      pair<ll, ll> tmp;
      int h, m, s;
      scanf("%d:%d:%d", &h, &m, &s);
      tmp.first = (ll)(h * 3600 + m * 60 + s);
      scanf("%d:%d:%d", &h, &m, &s);
      tmp.second = (ll)(h * 3600 + m * 60 + s);
      t.push_back(tmp);
    }

    sort(t.begin(), t.end());

    ll ans = 0, movin = 0, ind = 0;
    vector<ll> q;
    for(ll now=0; now <= ADAY; now++){
      while(!q.empty() && now == q[0]){
        movin--;
        q.erase(q.begin());
      }
      while(ind < n && now == t[ind].first){
        q.push_back(t[ind].second);
        sort(q.begin(), q.end());
        movin++;
        ind++;
        ans = max(ans, movin);
      }
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #ifndef _WIN32
#include<iostream>
#endif // !_WIN32

#include<algorithm>
#include<vector>
#include<string>
#include<iomanip>
#include<map>
using namespace std;
#define FOR(i,bg,ed) for(int i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
int main() {
	int N;
	while (cin >> N, N) {
		vector<string> s;
		REP(i,N){
			string t;
			cin >> t;
			s.push_back(t + "1");
			cin >> t;
			s.push_back(t + "0");
		}
		sort(ALL(s));
		int lb = 0;
		int ub = N;
		auto f = [&](int cnt) {
			for (auto &it : s) {
				if (it.back() == '1')cnt--; else cnt++;
				if (cnt < 0)return false;
			}
			return true;

		};
		while (ub - lb > 1) {
			const int mid = (lb + ub) / 2;
			if (f(mid))ub = mid;
			else lb = mid;
		}
		cout << ub << endl;
	}

}

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;
        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));
        }

        int cnt = 1;
        vector< bool > dep(n, false);
        vector< bool > used(n, false);
        dep[0] = true;
        for(int i = 0; i < n; i++) {
            used[i] = true;
            if(dep[i]) {
                for(int j = i + 1; j < n; j++) {
                    if(!used[j] && v[i].second > v[j].first) {
                        cnt++;
                        used[j] = true;
                        dep[j] = true;
                    }
                }
            }
        }
        cout << cnt << endl;
    }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cstdio>
#include <queue>
#include <stack>
#include <map>
#include <set>

#define rep(i, n) for(int i = 0; i < (n); i++)
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define all(v) (v).begin(), (v).end()
#define rev(s) string((s).rbegin(), (s).rend())
#define MP make_pair
#define X first
#define Y second

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

int main(){
	while(1){
		int n;
		cin >> n;
		if(!n)break;

		priority_queue<int, vector<int>, greater<int> > lq;
		priority_queue<int, vector<int>, greater<int> > aq;

		rep(i, n){
			int h, m, s;
			scanf("%d:%d:%d", &h, &m, &s);
			lq.push(h*60*60+m*60+s);
			scanf("%d:%d:%d", &h, &m, &s);
			aq.push(h*60*60+m*60+s);
		}

		int wait = 0;
		int need = 0;
		rep(i, 60*60*24){
			if(!aq.empty() && aq.top() <= i){
				wait++;
				aq.pop();
			}
			if(!lq.empty() && lq.top() <= i){
				if(wait <= 0){
					need++;
					wait++;
				}
				wait--;
				lq.pop();
			}
		}
		cout << need << endl;
	}

	return 0;
}