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>
#include <queue>
#include <algorithm>
#define INF 1 << 28
using namespace std;

typedef pair<int,int> P;

int main ()
{
    int n;
    while (cin >> n, n) {
        string str1, str2;
        vector<P> time;
        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 * 60 * 60 + t2 * 60 + t3;
            ss2 >> t1 >> t2 >> t3;
            int e = t1 * 60 * 60 + t2 * 60 + t3;

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

        st.push_back(INF);
        et.push_back(INF);
        sort(st.begin(), st.end());
        sort(et.begin(), et.end());

        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 <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <ostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#define INF 1000000000
#define rep(i,a,b) for (int i=(a);i<(b);i++)
#define rev(i,a,b) for (int i=(a)-1;i>=b;i--)
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef queue<int> qi;
typedef vector<int> vi;
typedef vector<string> vs;
int dx[4] = { 0, 1, 0, -1 };
int dy[4] = { 1, 0, -1, 0 };

int t[86401];

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	while(true) {
		int n;
		cin >> n;
		if(n == 0) break;

		memset(t,0,sizeof(t));
		rep(i,0,n) {
			int h,m,s;
			scanf("%d:%d:%d", &h, &m, &s);
			t[h*3600 + m*60 + s]++;
			scanf("%d:%d:%d", &h, &m, &s);
			t[h*3600 + m*60 + s]--;
		}

		int ans = -1, tmp = 0;
		rep(i,0,86401) {
			tmp += t[i];
			if(ans < tmp) ans = tmp;
		}
		cout << ans << endl;
	}

	return 0;
}

C++: #include "bits/stdc++.h"

#define REP(i, n, N) for(ll i=(n); i<(N); i++)
#define RREP(i, n, N) for(ll i=(N-1); i>=n; i--)
#define SPACEREP(lst,itr) for(auto itr=lst.begin(); itr!=lst.end();++itr){cout<<*itr<<(++itr!=anslist.end()?" ":"\n");itr--;}
#define CK(n, a, b) ((a)<=(n)&&(n)<(b))
#define ALL(v) (v).begin(),(v).end()
#define MCP(a, b) memcpy(b,a,sizeof(b))
#define p(s) cout<<(s)<<endl
#define p2(a, b) cout<<(a)<<" "<<(b)<<endl
#define v2(T) vector<vector<T>>
typedef long long ll;
using namespace std;
const ll mod = 1e9 + 7;
const ll inf = 1e18;

int convert(string s){
    int hh,mm,ss;
    hh = ((s[0]-'0')*10+(s[1]-'0'))*60*60;
    mm = ((s[3]-'0')*10+(s[4]-'0'))*60;
    ss = ((s[6]-'0')*10+(s[7]-'0'));
    return hh+mm+ss;
}

int main(){
    int n,start,end;
    string s;
    list< list<int> > inputs;
    while(1){
        cin >> n;
        if(n==0)break;
        list<int> tmp={};
        REP(i,0,n){
            cin >> s;
            start = convert(s);
            cin >> s;
            end = convert(s);
            tmp.push_back(start);
            tmp.push_back(end);
        }
        inputs.push_back(tmp);
    }

    for(auto x : inputs){
        int time[86401]={0};
        int ans=0;
        for(auto itr=x.begin();itr!=x.end();itr++){
            time[*itr]+=1;
            itr++;
            time[*itr]-=1;
        }
        ans=max(time[0],ans);
        REP(i,1,86400){
            time[i]+=time[i-1];
            ans=max(time[i],ans);
        }
        p(ans);
    }
    
}

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

int main(){
  int a,h,m,s,sum,r;
  char c;
  vector<pair<int,int> > vp;
  pair<int,int> p;
  while(1){
    cin>>a;
    vp.clear();
    if(a==0)break;
    for(int i=0;i<a;i++){
      cin>>h>>c>>m>>c>>s;
      h=h*3600+m*60+s;
      p.first=h;p.second=1;
      vp.push_back(p);
      cin>>h>>c>>m>>c>>s;
      h=h*3600+m*60+s;
      p.first=h;p.second=-1;
      vp.push_back(p);
    }
    sort(vp.begin(),vp.end());
    r=0;
    sum=0;
    for(int i=0;i<vp.size();i++){
      r+=vp[i].second;
      if(r>sum)sum=r;
    }
    cout<<sum<<endl;
  }
  return 0;
}