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 <algorithm>
#include <cstdio>

using namespace std;

struct P {
	int s, e;
	P() {};
	P(int s, int e) : s(s), e(e) {}
};
bool operator <(const P& p1, const P& p2) {
	return p1.e < p2.e;
}

int GetTime() {
	int h, m, s;
	scanf("%d:%d:%d", &h, &m, &s);
	return (h * 60 + m) * 60 + s;
}
int main() {
	int n;
	while ( cin >> n, n ) {
		vector<P> v;
		for (int i = 0; i < n; ++i) {
			int s = GetTime();
			int e = GetTime();
			v.push_back( P(s, e) );
		}
		sort( v.begin(), v.end() );

		vector<int> ans;
		for (int i = 0; i < n; ++i) {
			int pos = -1;
			for (int j = 0; j < ans.size(); ++j) {
				if (ans[j] <= v[i].s) {
					pos = j;
					break;
				}
			}
			if (pos < 0) {
				ans.push_back(v[i].e);
			}
			else {
				ans[pos] = v[i].e;
			}
/*			vector<int>::iterator it = upper_bound(ans.begin(), ans.end(), v[i].s);
			if (it == ans.begin() || --it == ans.begin() ) {
				ans.push_back(v[i].e);
			}
			else {
				*it = v[i].e;
			}
*/
		}
		cout << ans.size() << endl;
	}
}

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

#define CH(N,A,B) (A<=N&&N<B)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define RREP(i,a,b) for(int i=(b-1);a<=i;i--)

using namespace std;

int d[10000000], n, hhS, mmS, ssS, hhG, mmG, ssG;

int main() {
  while(1){
    cin>>n;
    if(n==0) break;
    REP(i,1,24*60*60+2) d[i] = 0;
    REP(i,0,n){
      scanf("%d:%d:%d %d:%d:%d", &hhS, &mmS, &ssS, &hhG, &mmG, &ssG);
      d[hhS*(60*60) + mmS*60 + ssS]++;
      d[hhG*(60*60) + mmG*60 + ssG]--;
      //test
      //cout<<"hhS "<<hhS<<", mmS "<<mmS<<", ssS "<<ssS<<endl;
    }
    int ans = 0;
    REP(i,1,24*60*60+2){
      d[i] += d[i-1];
      ans = max(ans, d[i]);
    }
    cout<<ans<<endl;
  }

  return 0;
}

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

#define MOD7 1000000007
#define MOD9 1000000009

#define rep(i, n) for (int i = 0; i < (n); i++)
#define REP(i, a, n) for (int i = (a); i <= (n); i++)
#define all(a) (a).begin(), (a).end()

using namespace std;

int dx[4] = { 1, 0, -1, 0 };
int dy[4] = { 0, -1, 0, 1 };

int nextInt() {int a; cin >> a; return a;}
char nextChar() {char a; cin >> a; return a;}
double nextDouble() {double a; cin >> a; return a;}
string nextString() {string a; cin >> a; return a;}

void inputVector(vector<int> &v, int &n) {rep(i,n){v.push_back(nextInt());}}
void inputVector(vector<double> &v, int &n) {rep(i,n){v.push_back(nextDouble());}}
void inputVector(vector<string> &v, int &n) {rep(i,n){v.push_back(nextString());}}

int memo[86500];

int timeToInt(string s) {
    int ret = 0;
    ret += (s[0] - '0') * 36000;
    ret += (s[1] - '0') * 3600;
    ret += (s[3] - '0') * 600;
    ret += (s[4] - '0') * 60;
    ret += (s[6] - '0') * 10;
    ret += (s[7] - '0') * 1;
    return ret;
}

signed main() {
    int n;
    while (cin >> n) {
	if (!n) break;

	memset(memo, 0, sizeof(memo));

	rep(i, n) {
	    string s, t;
	    cin >> s >> t;
	    int t1 = timeToInt(s), t2 = timeToInt(t);
	    memo[t1]++;
	    memo[t2]--;
	}
	REP(i, 1, 86400) {
	    memo[i] += memo[i - 1];
	}
	int ret = 0;
	rep(i, 86450) ret = max(ret, memo[i]);
	cout << ret << endl;
    }

    return 0;
}

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

#define dump(x) cout << (x) << '\n'
#define Int int64_t
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()

Int INF = 1e18;
int inf = 1e9;
Int mod = 1e9+7;

int main() {
    vector<int> res;
    while (true) {
        int n;
        cin >> n;
        if (n == 0) break;
        vector<int> h(n * 2), m(n * 2), s(n * 2);
        for (int i = 0; i < n * 2; i++) {
            char a, b;
            cin >> h[i] >> a >> m[i] >> b >> s[i];
        }
        vector<int> time(24 * 60 * 60 + 1, 0);
        for (int i = 0; i < n * 2; i++) {
            int sec = h[i] * 3600 + m[i] * 60 + s[i];
            if (i % 2 == 0) {
                time[max(sec, 0)]++;
            }
            else {
                time[min(sec, 24 * 60 * 60)]--;
            }
        }
        for (int i = 0; i < 24 * 60 * 60; i++) {
            time[i + 1] += time[i];
        }
        int ma = -1;
        for (int i = 0; i < 24 * 60 * 60; i++) {
            if (ma < time[i]) {
                ma = time[i];
            }
        }
        res.push_back(ma);
    }
    for (int i = 0; i < (int)res.size(); i++) {
        dump(res[i]);
    }
    return 0;
}