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<bits/stdc++.h>
#define INF 2000000000
#define int long long int
#define MOD 1000000007
#define pb push_back
#define cin1(n) (cin >> n)
#define cin2(a,b) (cin >> a >> b)
#define cin3(a,b,c) (cin >> a >> b >> c)
#define cout(n) (cout << n << endl)
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define fr first 
#define sc second 
#define EPS (1e-10)

using namespace std;

typedef vector<int> vi;
typedef vector< vector<int> > vvi;
typedef vector<pair<int,int>> vpii;
typedef vector<string> vs;
typedef vector<vector<string>> vss;
typedef pair<int,int> pii;

int dx[] = {1,-1,0,0};
int dy[] = {0,0,1,-1};
int n,m;
int a,b;
int p,q;

pii input(string t1,string t2) {
	int ret1,ret2;

	ret1 = stoi(t1.substr(6,2)) + 60 * stoi(t1.substr(3,2)) + 60 * 60 * stoi(t1.substr(0,2));
	ret2 = stoi(t2.substr(6,2)) + 60 * stoi(t2.substr(3,2)) + 60 * 60 * stoi(t2.substr(0,2));
	return make_pair(ret1,ret2);
}

signed main() {

	while(1) {
		cin1(n);
		if (n == 0) break;

		vpii table(n,make_pair(0,0));
		rep(i,0,n) {
			string time1,time2;
			cin2(time1,time2);
			table[i] = input(time1,time2);	
		}

		sort(table.begin(),table.end());
		
		int idx = 0;
		vector<pair<bool,int>> train;
		train.pb(make_pair(true,0));
		rep(i,0,60*60*24) {
			rep(j,0,train.size()) {
				if (train[j].sc == i) {
					train[j].fr = true;
					train[j].sc = 0;
				}
			}
			if (table[idx].fr == i) {
				bool flag = false;
				rep(j,0,train.size()) {
					if (train[j].fr) {
						train[j].fr = false;
						train[j].sc = table[idx].sc;
						flag = true;
						break;
					}
				}
				if (!flag) {
					train.pb(make_pair(false,table[idx].sc));
				}
				idx++;
				i--;
			}
		}
		cout(train.size());
	}

	return 0;
}

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

double a[100000];

double rec(int n,double k){
  double tmp,ans;
  if(n<1)return 0.0;
  if(n==1)return 1.0;
  tmp = k/2;

  ans = 1.0;
  ans += tmp * rec(n-1,tmp);
  if(!a[n-2])a[n-2] = rec(n-2,1.0);
  ans += (1.0-tmp) * a[n-2];

  return ans;
}

int main(){
  int n;
  double d;

  while(1){
    cin >> n;
    if(!n)break;
    for(int i=0;i<=n;i++)a[i] = 0;
    d = rec(n,1.0);
    cout << d << endl;
  }
}

C++: #include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <list>
#include <tuple>
#include <bitset>

using namespace std;

inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
inline bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
template<class T> inline T sqr(T x) { return x*x; }

typedef pair<int, int> P;
typedef tuple<int, int,int> T;
typedef long long ll;
typedef unsigned long long ull;

#define For(i,a,b)	for(int (i) = (a);i < (b);(i)++)
#define rep(i,n)	For(i,0,n)
#define clr(a)		memset((a), 0 ,sizeof(a))
#define mclr(a)		memset((a), -1 ,sizeof(a))
#define all(a)		(a).begin(),(a).end()
#define sz(a)		(sizeof(a))
#define Fill(a,v)	fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v)

const int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, -1, 0, 1, -1, 1, -1, 1 };
const int mod = 1000000007;
const int INF = 1e9;

int d[100000];

int main()
{

	int n;
	while (cin >> n && n){
		clr(d);
		rep(i, n){
			string S, E;
			cin >> S >> E;

			int s = toInt(S.substr(0, 2)) * 3600 + toInt(S.substr(3, 2)) * 60 + toInt(S.substr(6, 2));
			int e = toInt(E.substr(0, 2)) * 3600 + toInt(E.substr(3, 2)) * 60 + toInt(E.substr(6, 2));

			For(i, s, e){
				d[i]++;
			}
		}

		int ans = 0;
		rep(i, 100000){
			ans = max(d[i], ans);
		}
		cout << ans << endl;
	}

	return 0;
}

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

int main() {
    int n;
    while (cin >> n, n != 0) {
        vector<int> imos(100000, 0);
        for (int i=0; i<n; i++) {
            int h, m, s, start, goal;
            char colon;
            cin >> h >> colon >> m >> colon >> s;
            start = s + m*60 +h*60*60;
            cin >> h >> colon >> m >> colon >> s;
            goal = s + m*60 +h*60*60;

            imos[start] += 1;
            imos[goal]  -= 1;
        }
        int sum = 0;
        for (int i=0; i<100000; i++) {
            sum += imos[i];
            imos[i] = sum;
        }
        cout << *max_element(imos.begin(), imos.end()) << endl;
    }
}