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 <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <algorithm>

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

using namespace std;
typedef long long ll;

int main()
{
    int n;
    while(cin >> n && n) {

        vector<string> v;
        string s,t;
        cin >> s >> t;

        v.push_back(t);

        rep(i,n-1) {
            cin >> s >> t;

            bool flag = true;
            rep(j,v.size()) {
                if(v[j] <= s) {
                    v[j] = t;
                    flag = false;
                    break;
                }
            }

            if(flag) v.push_back(t);
        }

        cout << v.size() << endl;
    }

    return 0;
}

C++: #define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	for (;;) {
		int n; cin >> n;
		if (n == 0) break;
		vector<int> a(86400);
		while (n--) {
			int h1, m1, s1, h2, m2, s2;
			scanf("%d:%d:%d %d:%d:%d", &h1, &m1, &s1, &h2, &m2, &s2);
			a[h1 * 3600 + m1 * 60 + s1]++;
			a[h2 * 3600 + m2 * 60 + s2]--;
		}
		int x = 0, maxi = 0;
		for (int t = 0; t < 86400; t++) {
			x += a[t];
			maxi = max(maxi, x);
		}
		cout << maxi << endl;
	}
}

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

const int TIME = 60 * 60 * 24 + 60 * 60 + 70;
int data[TIME];

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	
	int n;
	while(cin >> n && n != 0){
		for(int i = 0; i < TIME; ++i){
			data[i] = 0;
		}
		
		int a, b, c;
		for(int i = 0; i < n; ++i){
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 3600 + b * 60 + c] ++;
			
			scanf("%d:%d:%d", &a, &b, &c);
			data[a * 3600 + b * 60 + c] --;
		}
	
		int ans = 0;
		for(int i = 0; i < TIME; ++i){
			if(i > 0)
				data[i] += data[i - 1];
			ans = max(ans, data[i]);
		}
		
		cout << ans << endl;
	}
	return 0;
}

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

using namespace std;
int N;
string In[10000], Out[10000];
int main() {
  while (cin >> N && N > 0) {
    for (int i=0; i<N; ++i) {
      cin >> Out[i] >> In[i];
    sort(In, In+N);
    sort(Out, Out+N);
    //    for (int i=0; i<N; ++i)
    //      cout << Out[i] << ' ' << In[i] << endl;
  }

  int p=0, taiki=0, train=0;
  for (int i=0; i<N; ++i) {
    while (p<N && In[p] <=Out[i]) {
      taiki++;
      p = p+1;
    }
    if (taiki > 0) taiki = taiki - 1;
    else train = train + 1;
  }
  cout << train << endl;
}
}

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

using namespace std;

int main(void) {
  int n;
  while (cin >> n, n) {
    int h[2], m[2], s[2], run[60 * 60 * 24 + 1] = {};
    for (int i = 0; i < n; i++) {
      for (int i = 0; i < 2; i++) {
        scanf("%02d:%02d:%02d", &h[i], &m[i], &s[i]);
      }
      for (int i = 0; i < 2; i++) {
        int t = h[i] * 3600 + m[i] * 60 + s[i];
        run[t] += i ? -1 : 1;
      }
    }

    int ans = 0;
    for (int i = 1; i <= 60 * 60 * 24; i++) {
      run[i] += run[i - 1];
      ans = max(ans, run[i]);
    }

    cout << ans << endl;
  }

  return 0;
}

C++: #define D(x) cout << #x " = " << x << endl
#define DD(x, y) cout << "(" #x ", " #y ") = (" << x << ", " << y << ")" << endl
#define DDD(x, y, z) cout << "(" #x ", " #y ", " #z ") = (" << x << ", " << y << ", " << z << ")" << endl
#define DV(v) for (auto __macro_vi : v){ cout << __macro_vi << " ";} cout << endl;
#define DA(a, n) for (int __macro_i = 0; __macro_i < n; ++__macro_i) { cout << a[__macro_i] << " "; } cout << endl;
#define REP(i, n) for (int i = 0; i < n; ++i)
#define ALL(v) (v).begin(), (v).end()
#include<iostream>
#include<vector>
#include<cassert>
#include<cmath>
#include<algorithm>

using namespace std;

int read() {
    int h, m, s;
    char c;
    cin >> h >> c >> m >> c >> s;
    return h * 3600 + m * 60 + s;
}
using P = pair<int, int>;
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    while(1) {
        int n;
        cin >> n;
        if (n == 0) break;
        vector<P> v;
        REP(i, n) {
            v.emplace_back(read(), 1);
            v.emplace_back(read(), 0);
        }
        sort(v.begin(), v.end());
        int ans = 0;
        int cnt = 0;
        for (auto vi : v) {
            if (vi.second == 1) {
                cnt += 1;
            } else {
                cnt -= 1;
            }
            ans = max(ans, cnt);
        }
        cout << ans << endl;
    }
}