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>
using namespace std;
using ll=long long;
using vb=vector<bool>;
using vvb=vector<vb>;
using vd=vector<double>;
using vvd=vector<vd>;
using vi=vector<int>;
using vvi=vector<vi>;
using vl=vector<ll>;
using vvl=vector<vl>;
using pii=pair<int,int>;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll>;
using tlll=tuple<ll,ll,ll>;
using vs=vector<string>;

#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define rep(i,n) range(i,0,n)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define range(i,a,n) for(int i=(a);i<(n);i++)

#define LINF ((ll)1ll<<60)
#define INF ((int)1<<30)
#define EPS (1e-9)
#define MOD (1000000007ll)
#define fcout(a) cout<<setprecision(a)<<fixed
#define fs first
#define sc second
#define PI 3.1415926535897932384

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

template<class T>bool chmax(T&a,T b){if(a<b){a=b; return true;}return false;}
template<class T>bool chmin(T&a,T b){if(a>b){a=b; return true;}return false;}
template<class S>S acm(vector<S>&a){return accumulate(all(a),S());}
template<class S>S max(vector<S>&a){return *max_element(all(a));}
template<class S>S min(vector<S>&a){return *min_element(all(a));}
void YN(bool b){cout<<(b?"YES":"NO")<<"\n";}
void Yn(bool b){cout<<(b?"Yes":"No")<<"\n";}
void yn(bool b){cout<<(b?"yes":"no")<<"\n";}

ll max(int a,ll b){return max((ll)a,b);} ll max(ll a,int b){return max(a,(ll)b);}
template<class T>void puta(T&&t){cout<<t<<"\n";}
template<class H,class...T>void puta(H&&h,T&&...t){cout<<h<<' ';puta(t...);}
template<class S,class T>ostream&operator<<(ostream&os,pair<S,T>p){os<<"["<<p.first<<", "<<p.second<<"]";return os;};
template<class S>auto&operator<<(ostream&os,vector<S>t){bool a=1; for(auto s:t){os<<(a?"":" ")<<s;a=0;} return os;}

void solve(int n){
	int h,m,s,ans=0;
	vi v(100000,0);
	rep(i,n){
		scanf("%d:%d:%d",&h,&m,&s);
		v[h*3600+m*60+s]++;
		scanf("%d:%d:%d",&h,&m,&s);
		v[h*3600+m*60+s]--;
	}
	range(i,1,100000){
		v[i]+=v[i-1];
		chmax(ans,v[i]);
	}
	cout<<ans<<endl;
}

int main(){
	//cin.tie(0);
	//ios::sync_with_stdio(false);
	int n;
	while(cin>>n,n)solve(n);
}

C++: #include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <fstream>
 
using namespace std;
 
#define INF 100000000
#define EPS 1e-9
#define PI acos(-1)
 
typedef long long ll;
typedef pair<int, int> P;

#define MAX_N 10000

int n;
int v[60*60*24 + 5];

vector<int> ans_list;

int conv(string str){
  string hh,mm,ss;
  hh += str[0];
  hh += str[1];
  mm += str[3];
  mm += str[4];
  ss += str[6];
  ss += str[7];

  return atoi(hh.c_str()) * 3600 + atoi(mm.c_str()) * 60 + atoi(ss.c_str());

}

int main(){

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

    memset(v,0,sizeof(v));
    string str1, str2;

    for(int i = 0; i < n; i++){
      cin >> str1 >> str2;
      v[conv(str1)]++;
      v[conv(str2)]--;
    }

    int ans = 0;
    int tmp = 0;
    for(int i = 0; i <= 60*60*24+1; i++){
      tmp += v[i];
      ans = max(ans,tmp);
    }

    ans_list.push_back(ans);

  }

  for(int i = 0; i < ans_list.size(); i++){
    cout << ans_list[i] << endl;
  }

  return 0;

}

C++: #include <algorithm>
#include <cstdio>
#include <iostream>
#include <string>
#include <utility>
#include <vector>
using namespace std;
int main() {
  int n, ans, k, t[6];
  vector< pair<int, int> > T;
  while (cin >> n, n) {
    for (int i = 0; i < n; ++i) {
      scanf("%d:%d:%d %d:%d:%d",&t[0],&t[1],&t[2],&t[3],&t[4],&t[5]);
      T.push_back(make_pair(t[0]*3600+t[1]*60+t[2], 1));
      T.push_back(make_pair(t[3]*3600+t[4]*60+t[5], -1));
    }
    ans = 0;
    k = 0;
    sort(T.begin(), T.end());
    for (int i = 0; i < 2*n; ++i) {
      k += T[i].second;
      ans = max(ans, k);
    }
    cout << ans << endl;
    T.erase(T.begin(), T.end());
  }
  return 0;
}

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

int sum[60 * 60 * 24];
int main() {
    int n;
    while(cin >> n, n) {
        for(int i = 0; i < 60 * 60 * 24; i++) sum[i] = 0;
        for(int i = 0; i < n; i++){
            int h1, m1, s1, h2, m2, s2;
            scanf("%02d:%02d:%02d", &h1, &m1, &s1);
            scanf("%02d:%02d:%02d", &h2, &m2, &s2);
            int t1 = h1 * 60 * 60 + m1 * 60 + s1;
            int t2 = h2 * 60 * 60 + m2 * 60 + s2; 
            for(int i = t1; i < t2; i++) sum[i]++;
        }
        int ans = 0;
        for(int i = 0; i < 60 * 60 * 24; i++){
            ans = max(ans, sum[i]);
        }
        cout << ans << endl;
    }
    return 0;
}