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 <sstream>
#include <string>
#include <cstring>
#include <vector>
#include <algorithm>
#include <tuple>
#include <queue>
#include <set>
#include <cstdio>
#include <climits>
#include <cmath>
#include <array>
#include <functional>
#include <sstream>
#include <list>
#include <set>
const int MOD=1000000007;
const int INF=1000000000;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
const double eps=1e-9;
const int inf=1e9;
typedef pair<int,int> P;
struct Point
{
  double x,y;
  Point(){x=0;y=0;}
  Point(double d_x,double d_y){x=d_x,y=d_y;}
  double operator*(Point obj){return obj.x*x+obj.y*y;}
  double operator%(Point obj){return obj.y*x-obj.x*y;}
  Point operator*(double b){Point tmp;tmp.x=x*b;tmp.y=y*b;return tmp;}
  Point operator/(double b){Point tmp;tmp.x=x/b;tmp.y=y/b;return tmp;}
  Point operator+(Point obj){Point tmp;tmp.x=x+obj.x;tmp.y=y+obj.y;return tmp;}
  Point operator-(){Point tmp;tmp.x=-x;tmp.y=-y;return tmp;}
  Point operator-(Point obj){Point tmp;tmp.x=x-obj.x;tmp.y=y-obj.y;return tmp;}
  Point operator-=(Point obj){x-=obj.x;y-=obj.y;return *this;}
  Point operator+=(Point obj){x+=obj.x;y+=obj.y;return *this;}
  Point operator/=(double b){x=x/b;y=y/b;return *this;}
  Point operator*=(double b){x=x*b;y=y*b;return *this;}
  double size(){return hypot(x,y);}
  Point unit(){return Point(x/size(),y/size());}
  Point normal(){return Point(y,-x);}
  double atan(){return atan2(y,x);}
};

bool operator<(Point a,Point b){return a.x!=b.x?a.x<b.x:a.y<b.y;}
bool operator>(Point a,Point b){return b<a;}
bool operator<=(Point a,Point b){return !(b<a);}
bool operator>=(Point a,Point b){return !(a<b);}
bool operator==(Point a,Point b){return (a-b).size()<eps;}
bool operator!=(Point a,Point b){return !(a==b);}

bool equal(double a,double b){return abs(a-b)<eps;}
double cross(Point a,Point b){return a%b;}
double dot(Point a,Point b){return a*b;}

int ccw(Point a,Point b,Point c)
{
  b=b-a;
  c=c-a;
  if(b%c>0) return +1;
  else if(b%c<0)return -1;
  else if(b*c<0) return +2;
  else if(b.size()<c.size()) return -2;
  else return 0;
}


int times[100005];
int n;

void calc(string str,int v)
{
  stringstream ss(str);
  int h,m,s;
  char c;
  ss >> h >> c >> m >> c >> s;
  times[h*60*60+m*60+s]+=v;
}


int main(int argc,char const* argv[])
{
  while(1)
    {
      memset(times,0,sizeof(times));
      cin >> n;
      if(!n)break;
      for(int i=0;i<n;i++)
	{
	  string start,goal;
	  cin >> start >> goal;
	  calc(start,1);
	  calc(goal,-1);
	}
      for(int i=1;i<100000;i++)
	{
	  times[i]+=times[i-1];
	}
      int ans=0;
      for(int i=0;i<100000;i++)
	{
	  ans=max(ans,times[i]); 
	}
      cout << ans << endl;
    }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int n,s,t,cnt,ans; string S;
vector<pair<int,int>> trains;
vector<int> unit={36000,3600,0,600,60,0,10,1};
multiset<int> waiting;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    while(cin >> n,n){
        trains.clear();
        for (int i=0;i<n;++i){
            for (int j=0;j<2;++j){
                cin >> S; cnt=0;
                for (int k=0;k<8;++k){
                    if (k%3==2) continue;
                    cnt+=(S[k]-'0')*unit[k];
                }
                (!j?s:t)=cnt;
            }
            trains.emplace_back(s,t);
        }
        sort(trains.begin(),trains.end());
        waiting.clear();
        ans=0;
        for (int i=0;i<n;++i){
            auto itr=waiting.upper_bound(trains[i].first);
            if (itr==waiting.begin()) ++ans;
            else {waiting.erase(--itr);}
            waiting.insert(trains[i].second);
        }
        cout << ans << '\n';
    }
}

C++: #include<iostream>
#include<string>
#include<queue>
using namespace std;
int main(){
  while(1){
    int n;
    string a[10001],b;
    priority_queue<string,vector<string>,greater<string> > c;
    cin>>n;
    if(n==0)break;
    for(int i=0;i<n;i++){
      cin>>a[i]>>b;
      c.push(b);
    }
    int cnt=0;
    for(int i=0;i<n;i++){
      if(a[i]>=c.top()){
	c.pop();
      }else cnt++;
    }
    cout<<cnt<<endl;
    while(c.empty())c.pop();
  }
  return 0;
}