1 #include <cstdio>
 2 #include <iostream>
 3 #include <algorithm>
 4 using namespace std;
 5 
 6 int a[111],b[111];
 7 int n,end,cnt;
 8 
 9 int main ()
10 {
11     int i,j;
12     while (scanf ("%d",&n),n)
13     {
14         for (i=0; i<n; i++)
15         scanf ("%d %d",&a[i],&b[i]);
16         for (i=0; i<n; i++)
17         for (j=i; j<n; j++)
18         {
19             if (b[i] > b[j])
20             {
21                 swap(b[i], b[j]);
22                 swap(a[i], a[j]);//交换函数
23             }
24         }
25         cnt = 1;
26         end = b[0];
27         for (i=1; i<n; i++)
28         {
29             if (a[i] >= end)
30             {
31                 cnt++;
32                 end = b[i];
33             }
34         }
35         printf ("%d\n",cnt);
36     }
37     return 0;
38 }