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 <cmath>
#include <iostream>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <algorithm>
#include <utility>
#include <iomanip>

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

using namespace std;

typedef pair<int, int> P;

const int INF = 1e15;
const int MOD = 1e9+7;

int seconds(string t){
    int h = (t[0] - '0') * 10 + t[1] - '0';
    int m = (t[3] - '0') * 10 + t[4] - '0';
    int s = (t[6] - '0') * 10 + t[7] - '0';

    return h * 60 * 60 + m * 60 + s;
}

signed main(){
    while(true){
        int n;
        cin >> n;

        if(n == 0){
            break;
        }

        vector<int> time(90000);
        rep(i, n){
            string s, t;
            cin >> s >> t;
            int begin = seconds(s);
            int end = seconds(t);

            time[begin] += 1;
            time[end] -= 1;
        }

        rep(i, 90000 - 1){
            time[i+1] += time[i];
        }

        int ans = 0;
        rep(i, 90000){
            if(time[i] > ans){
                ans = time[i];
            }
        }
        cout << ans << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
#include <functional>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<pint> vpint;
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)

void slove(int n){
	vector<int> v(86400);
	rep(i, 86400) v[i] = 0;//?????????
	rep(i, n){
		string s, e;
		cin >> s >> e;
		//?§???°?????????
		int start = 36000 * (s[0] - '0') + 3600 * (s[1] - '0') 
					+ 600 * (s[3] - '0') + 60 * (s[4] - '0')
					+ 10 * (s[6] - '0') + 1 * (s[7] - '0');
		int end = 36000 * (e[0] - '0') + 3600 * (e[1] - '0') 
					+ 600 * (e[3] - '0') + 60 * (e[4] - '0')
					+ 10 * (e[6] - '0') + 1 * (e[7] - '0');
		printf("%d %d\n", start, end);
		for (int j = start; j < end ; ++j) v[j]++;//???????????????
	}
	int ans;

	rep(i, 86400){
		ans = max(ans, v[i]);
	}
	//sort(all(v));
	//reverse(all(v));
	printf("%d\n", ans);
	return;
}
int main(void){
	rep(i, 1000000){
		int n; scanf("%d", &n);
		if(n == 0) break;
		slove(n);
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <cstring>
using namespace std;

int pop[24*3600+5];

inline int ss(char c) { return c-'0'; }

int stoi(string s) {
    return (ss(s[0])*10+ss(s[1]))*3600 + (ss(s[3])*10 + ss(s[4]))*60
        + ss(s[6])*10 + ss(s[7]);
}

int main() {
    int n;
    string s,t;
    while(cin>>n, n) {
        memset(pop, 0, sizeof(pop));
        for(int i=0; i<n; ++i) {
            cin>>s>>t;
            int ts = stoi(s), tt = stoi(t);
            for(int i=ts; i<tt; ++i) pop[i]++;
        }

        int ans = 0;
        for(int i=0; i<=24*3600; ++i) ans = max(ans, pop[i]);
        cout<<ans<<endl;
    }
}

C++: #include<bits/stdc++.h>
#define rep(i,n) for(int i=0; i<n; i++)
using namespace std;
int main(){
  int n;
  int Max = 24*3600+59*60+59;
  while(cin >> n,n){
    vector<int> v(Max+1,0);
    string s1,s2;
    rep(i,n){
     cin >> s1 >> s2;
     int sum1=0,sum2=0;
     for(int j=0; j<s1.size(); j+=3){
      if(j==0){
        sum1 += atoi(s1.substr(j,2).c_str())*3600;
        sum2 += atoi(s2.substr(j,2).c_str())*3600;
      }
      if(j==3){
        sum1 += atoi(s1.substr(j,2).c_str())*60;
        sum2 += atoi(s2.substr(j,2).c_str())*60;
      }
      if(j==6){
        sum1 += atoi(s1.substr(j,2).c_str());
        sum2 += atoi(s2.substr(j,2).c_str());
      }
     }
     v[sum1]++; v[sum2]--;
    }
    int ans = 0;
    rep(i,Max){
      v[i+1] += v[i];
      ans = max(ans,v[i+1]);
    }
    cout << ans << endl;
  }
  return 0;
}