#include <iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;
#define MAX 120
int N;
class Movie
{
public:
int start;
int end;
};
int compare(const void *a,const void *b)
{
return ((Movie*)a)->end-((Movie*)b)->end;
}
int main()
{
//freopen("in.txt","r",stdin);
while(scanf("%d",&N))
{
if(N==0)
return 0;
Movie m[MAX];
int i=0;
for(i=0;i<N;i++)
{
scanf("%d%d",&m[i].start,&m[i].end);
}
qsort(m,N,sizeof(Movie),compare);
int j=0;
int tempstart=m[0].start;
int tempend=m[0].end;
int result=1;
for(i=1;i<N;i++)
{
if(tempend<=m[i].start)
{
tempstart=m[i].start;
tempend=m[i].end;
result++;
}
}
cout<<result<<endl;
}
return 0;
}