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;
#define rep(i,n) for (int (i)=(0);(i)<(int)(n);++(i))
using ll = long long;

int main() {

    int n;
    while (cin >> n, n) {

        int hws[24][60][60];
        rep(i, 24) rep(j, 60) rep(k, 60) hws[i][j][k] = 0;

        rep(i, n) {
            string s, e;
            cin >> s >> e;

            int h1 = stoi(s.substr(0, 2));
            int m1 = stoi(s.substr(3, 2));
            int s1 = stoi(s.substr(6, 2));

            int h2 = stoi(e.substr(0, 2));
            int m2 = stoi(e.substr(3, 2));
            int s2 = stoi(e.substr(6, 2));

            hws[h1][m1][s1] += 1;
            hws[h2][m1][s1] -= 1;
        }

        int t = 0, ans = 0;
        rep(i, 24) rep(j, 60) rep(k, 60) {
            t += hws[i][j][k];
            ans = max(t, ans);
        }

        cout << ans << endl;

    }

}

C++: #include<iostream>
#include<ios>
using namespace std;
int get(){
	int h,m,s;
	scanf("%d:%d:%d",&h,&m,&s);
	return h*3600+m*60+s;
}
int n;
int cnt[90000];
int 
main()
{
	while(cin>>n,n)
	{
		for(int i=0;i<90000;i++)cnt[i]=0;
		for(int i=0;i<n;i++)
		{
			cnt[get()]++;cnt[get()]--;
		}
		int ans=cnt[0];
		for(int i=1;i<90000;i++)
		{
			cnt[i]+=cnt[i-1];
			ans=ans<cnt[i]?cnt[i]:ans;
		}
		cout<<ans<<endl;
	}
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int main() {
	int n;
	while (cin >> n, n) {
		int imos[86410] = {};
		for (int i = 0; i < n; i++) {
			int a, b, c, d, e, f; char ch;
			cin >> a >> ch >> b >> ch >> c;
			cin >> d >> ch >> e >> ch >> f;
			imos[a * 3600 + b * 60 + c]++;
			imos[d * 3600 + e * 60 + f]--;
		}
		int ans = imos[0];
		for (int i = 1; i <= 86400; i++) {
			imos[i] += imos[i - 1];
			ans = max(ans, imos[i]);
		}
		cout << ans << endl;
	}
}

C++: // clang-format off
#include <bits/stdc++.h>
#define int long long
#define main signed main()
// #define main int main()
#define loop(i, a, n) for (int i = (a); i < (n); i++)
#define rep(i, n) loop(i, 0, n)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define prec(n) fixed << setprecision(n)
#define stlice(from, to) substr(from, (to) - (from) + 1)
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second
using namespace std;
using pii = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vc = vector<char>;
using vb = vector<bool>;
using vs = vector<string>;
using vpii = vector<pii>;
using vvi = vector<vi>;
using vvb = vector<vb>;
using vvpii = vector<vpii>;
template<typename A> using fn = function<A>;
constexpr int INF = sizeof(int) == sizeof(long long) ? 1000000000000000000LL : 1000000000;
constexpr int MOD = 1000000007;
constexpr double PI = acos(-1);
template<typename A, typename B> bool cmin(A &a, const B &b) { return a > b ? (a = b, true) : false; }
template<typename A, typename B> bool cmax(A &a, const B &b) { return a < b ? (a = b, true) : false; }
constexpr bool odd(const int &n) { return n & 1; }
constexpr bool even(const int &n) { return !odd(n); }
void solve();
main { solve(); return 0; }
// clang-format on

void solve() {
  int n;
  while (cin >> n, n) {
    vi v(86400);
    rep(i, n) {
      int h, m, d;
      char gomi;
      cin >> h >> gomi >> m >> gomi >> d;
      int l = h * 3600 + m * 60 + d;
      cin >> h >> gomi >> m >> gomi >> d;
      int r = h * 3600 + m * 60 + d;
      v[l]++;
      v[r]--;
    }
    loop(i, 1, 86400) v[i] += v[i - 1];
    int c = 0;
    rep(i, 86400) cmax(c, v[i]);
    cout << c << endl;
  }
}

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

using namespace std;
const int MAX = 100000;
typedef pair<int,int> P;
int ans[MAX];

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

void init(){
  fill(ans,ans+MAX,0);
}

int main(){
  int n;
  while(cin >> n && n){
    init();
    for(int i = 0; i < n; i++){
      int hh,ss,mm;
      int hh2,ss2,mm2;
      scanf("%d:%d:%d",&hh,&ss,&mm);
      scanf("%d:%d:%d",&hh2,&ss2,&mm2);
      int from = ToS(hh,mm,ss);
      int to = ToS(hh2,mm2,ss2);
      for(int i = from; i < to; i++)
	ans[i]++;
    }
    
    int out = 0;
    for(int i = 0; i < MAX; i++)
      out = max(out,ans[i]);

    cout << out << endl;

  }
  return 0;
}

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

using namespace std;

using ll = long long;

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

#define INF 1e9

int main(void)
{
    int n, i, a, b, c, t[200000], Max;

    scanf("%d", &n);
    while(n != 0){
        for(i = 0; i < 200000; i++){
            t[i] = 0;
        }

        for(i = 0; i < n; i++){
            scanf("%d:%d:%d", &a, &b, &c);
            t[a * 3600 + b * 60 + c]++;
            scanf("%d:%d:%d", &a, &b, &c);
            t[a * 3600 + b * 60 + c]--;
        }

        Max = t[i];
        for(i = 1; i < 200000; i++){
            t[i] += t[i - 1];
            if(Max < t[i]){
                Max = t[i];
            }
        }

        printf("%d\n", Max);

        scanf("%d", &n);
    }
}