include<stdio.h>

include

using namespace std;

struct Pro
{
int sta;
int end;
}pro[100];

bool cmp(Pro a,Pro b)
{
if(a.end>b.end)return 0;
return 1;
}

int main()
{
int n;
while(scanf("%d",&n)!=EOF)
{
if(n==0)return 0;
for(int i=0;i<n;i++)
{
scanf("%d %d",&pro[i].sta,&pro[i].end);
}
sort(pro,pro+n,cmp);
int time=0,sum=0;
for(int i=0;i<n;i++)
{
if(pro[i].sta>=time)
{
time=pro[i].end;
sum++;
}
}
printf("%d\n",sum);
}
return 0;
}