#include <iostream>  
#include <algorithm>     
#define MAXN 100  
using namespace std; 

struct node {  
    int start;  
    int end;  
} record[MAXN];  
  
bool cmp(const node& a, const node& b)  
{  
    return (a.end<b.end);  
}  

int main()  
{  
    int n,count,lastend;  
    while(cin>>n && n)
    {
        for(int i=0; i<n; i++)  
            cin >> record[i].start >> record[i].end;
        sort(record,record + n,cmp);  
  
        // 贪心法处理：后一个起始时间必须大于或等于前一个终止时间  
        count = 0;  
        lastend = -1;  
        for(int i=0;i<n;i++) 
                {  
            if(record[i].start >= lastend) 
                        {  
                count++;  
                lastend = record[i].end;  
            }  
        }  
        cout << count << endl;  
    }  
}