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 <cstdio>
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <typeinfo>
#include <numeric>
#include <functional>
#include <unordered_map>
#include <bitset>


using namespace std;
using ll = long long;
using ull = unsigned long long;

const ll INF = 1e16;
const ll MOD = 1e9 + 7;

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




int main() {
    int n;
    cin >> n;
    
    while(n != 0){
        vector<int> imos(1e5);
        REP(i, n){
            int hh, mm, ss;
            
            scanf("%d:%d:%d", &hh, &mm, &ss);
            int t = hh * 3600 + mm * 60 + ss;
            imos[t]++;
            
            scanf("%d:%d:%d", &hh, &mm, &ss);
            t = hh * 3600 + mm * 60 + ss;
            imos[t]--;
        }
        
        int ans = imos[0];
        for(int i = 1; i < 1e5; i++){
            imos[i] += imos[i - 1];
            ans = max(ans, imos[i]);
        }
        cout << ans << endl;
        
        cin >> n;
    }
}

C++: #include<iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;

int main(){
	int n;
	int m[86400]={};
	while(cin >> n,n){
		for(int i=0;i<n;i++){
			int bh,bm,bs,eh,em,es;
			scanf("%d:%d:%d %d:%d:%d",&bh,&bm,&bs,&eh,&em,&es);
			m[(bh*60*60)+(bm*60)+bs]+=1;
			m[(eh*60*60)+(em*60)+es]+=-1;
		}
		int count=0,ans=1;
		for(int i=0;i<86400;i++){
			count+=m[i];
			ans=max(ans,count);
		}
		cout << ans << endl;
	}
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>
#include<cmath>
#include<cstring>
#include<queue>
#include<map>
#include<cstdio>
#include<climits>

#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)
using namespace std;
typedef pair<int, int> P;
typedef long long int ll;
typedef pair<ll,ll> LLP;
#define INF 1000000007
#define MOD 1000000007

#define ARRAY_MAX 100005

int d[ARRAY_MAX];

int main(){

    int n;
    while(cin >> n,n){
        int h,m,s;
        REP(i,n){
            scanf("%d:%d:%d",&h,&m,&s);
            d[24*h+60*m+s]++;
            scanf("%d:%d:%d",&h,&m,&s);
            d[24*h+60*m+s]--;
        }
        REP(i,ARRAY_MAX-1){
            d[i+1] += d[i];
        }
        int ans = 0;
        REP(i,ARRAY_MAX){
            ans = max(ans,d[i]);
        }
        cout << ans << endl;
    }


    return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

#define rep(i, n) for(int i=0; i<(n); ++i)
#define all(c) (c).begin(), (c).end()

template<typename T> inline void chmax(T& t, T f){if(t < f)t = f;}

int main(){
    int n;
    while(cin >> n, n){
        vector<pair<int, int> > events;
        events.reserve(n<<1);
        rep(i, n){
            int h1, m1, s1, h2, m2, s2;
            char d;
            cin >> h1 >> d >> m1 >> d >> s1 >> h2 >> d >> m2 >> d >> s2;
            events.emplace_back(3600 * h1 + 60 * m1 + s1, 1);
            events.emplace_back(3600 * h2 + 60 * m2 + s2, -1);
        }
        sort(all(events));
        int ans = 1, now = 0;
        rep(i, n<<1)chmax(ans, now += events[i].second);
        cout << ans << '\n';
    }
    return 0;
}

C++: #line 1 "/mnt/c/Users/leafc/dev/compro/lib/template.hpp"


#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
#define MM << " " <<

using namespace std;

template <class T> void say(bool val, T yes = "Yes", T no = "No") { cout << (val ? yes : no) << endl; }

template <class T> void chmin(T &a, T b) {
  if (a > b)
    a = b;
}

template <class T> void chmax(T &a, T b) {
  if (a < b)
    a = b;
}


#line 2 "tmp.cpp"

int calc2(string s) { return (s[0] - '0') * 10 + (s[1] - '0'); }

int calc(string s) {
  string h = s.substr(0, 2), m = s.substr(3, 2), sec = s.substr(6, 2);
  return calc2(h) * 3600 + calc2(m) * 60 + calc2(sec);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  while (true) {
    int n;
    cin >> n;
    if (n == 0)
      break;
    vector<int> imos(24 * 60 * 60, 0);

    REP(i, n) {
      string s, t;
      cin >> s >> t;
      imos[calc(s)]++;
      imos[calc(t)]--;
    }

    int size = imos.size();
    FOR(i, 1, size) { imos[i] += imos[i - 1]; }

    int ans = 0;
    REP(i, size) { chmax(ans, imos[i]); }
    cout << ans << endl;
  }
  return 0;
}