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 <string>
#include <sstream>
#include <vector>
#define INF 1 << 28
using namespace std;

int main ()
{
    int n;
    while (cin >> n, n) {
        string str1, str2;
        vector<int> st, et;
        while (n--) {
            cin >> str1 >> str2;
            for (int i = 0; i < str1.size(); i++) {
                if (str1[i] == ' ') {
                    str1[i] = str2[i] = ' ';
                }
            }

            stringstream ss1, ss2;
            ss1 << str1;
            ss2 << str2;

            int t1, t2, t3;
            ss1 >> t1 >> t2 >> t3;
            int s = t1 * 24 * 60 + t2 * 60 + t3;
            ss2 >> t1 >> t2 >> t3;
            int e = t1 * 24 * 60 + t2 * 60 + t3;

            st.push_back(s);
            et.push_back(e);
        }

        st.push_back(INF);
        et.push_back(INF);

        int k = 0, l = 0;
        int tmp = 0, MAX = 0;
        while (st[k] != INF || et[l] != INF) {
            if (st[k] < et[l]) {
                tmp++;
                k++;
            } else {
                tmp--;
                l++;
            }
            MAX = MAX < tmp ? tmp : MAX;
        }

        cout << MAX << endl;
    }

    return 0;
}

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

#define	mp	make_pair

using namespace std;

typedef	pair<int,bool>	pib;

int main(){
	for(int n;scanf("%d",&n),n;){
		static pib event[20000];
		for(int i=0;i<n;i++){
			for(int j=0;j<2;j++){
				int h,m,s;	scanf("%d%*c%d%*c%d",&h,&m,&s);
				event[2*i+j]=mp(3600*h+60*m+s,!j);	// departure: 1, arrival: 0
			}
		}

		sort(event,event+n);

		int train=0,maxtrain=-1;
		for(int i=0;i<2*n;i++){
			if(event[i].second==1)	train++;
			else	train--;
			maxtrain=max(maxtrain,train);
		}

		printf("%d\n",maxtrain);
	}

	return 0;
}

C++: #include <iostream>
#include <cstdio>
using namespace std;
int main(void){
    int n;
    int hh,mm,ss,st,en,t;
    int time[86401];
    char ch;
    while(1){
        cin >> n;
        if(n == 0)  break;
        for(int j = 0; j < 86400; j++){
            time[j] = 0;
        }
        for(int i = 0; i < n; i++){
            cin >> hh >> ch >> mm >> ch >> ss;
            st = hh * 3600 + mm * 60 + ss;
            cin >> hh >> ch >> mm >> ch >> ss;
            en = hh * 3600 + mm * 60 + ss;
            for(int j = st; j < en; j++){
                time[j]++;
            }
        }
        
        int maxt = 0;
        for(int i = 0; i < 86400; i++){
            if(maxt < time[i])  maxt = time[i];
        }
        
        cout << maxt << endl;
        
    }
    
    return 0;
}

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

using namespace std;

#define FOR(i,k,n) for(int i=(k); i<(int)n; ++i)
#define REP(i,n) FOR(i,0,n)
#define FORIT(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
typedef pair<int,int> P;
inline int tosc(int h, int m,int s){
  return h*3600 + m * 60 + s;
}

int main(){
  int n;
  while(cin>>n,n){
    P v[10001];
    REP(i,n){
      int h,m,s;
      scanf("%d:%d:%d",&h,&m,&s);
      int m1 = tosc(h,m,s);
      scanf("%d:%d:%d",&h,&m,&s);
      int m2 = tosc(h,m,s);
      v[i] = P(m1,m2);
    }
    sort(v , v + n);
    int ans = 0;
    priority_queue<int, vector<int>, greater<int> > que;
    REP(i,n){
      if(que.empty() || que.top() > v[i].first){
        ans++;
      }else{
        que.pop();
      }
      que.push(v[i].second);
    }
    cout<<ans<<endl;
  }
  return 0;
}

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][m2][s2] -= 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<cstdio>
#include<cstring>
#include<algorithm>
 
using namespace std;

int main(void){

  int n;
  int sum[3000];

  while(1){
        scanf("%d",&n);
        if(n==0)break;
        memset(sum,0,sizeof(sum));
        for(int i=0;i<n;i++){
            int h,m,s;
            scanf("%2d:%2d:%2d",&h,&m,&s);
            sum[h*60*60+m*60+s]++;
            scanf("%2d:%2d:%2d",&h,&m,&s);
            sum[h*60*60+m*60+s]--;
        }
        int res=sum[0];
        for(int i=0;i<=24*60*60;i++){
            sum[i+1]+=sum[i];
            res=max(res,sum[i+1]);
        }
        printf("%d\n",res);
    }
    return 0;
}