include<bits/stdc++.h>

using namespace std; struct meeting{

int s;
int e;

}meet[101]; int cmp(meeting a,meeting b){

return a.e<b.e;

} int main(){

int last,n;
int sum;
while(cin>>n){
	if(n==0) break;
	for(int i=0;i<n;i++){
		cin>>meet[i].s>>meet[i].e;
	}
	sort(meet,meet+n,cmp);
	sum=1;
	last=meet[0].e;
	for(int j=1;j<n;j++){
		if(meet[j].s>=last){
			sum++;
			last=meet[j].e;
		}
	}
	cout<<sum<<endl;
}
return 0;

}