poj1828

#include<iostream>
#include<algorithm>
using namespace std;
typedef struct Node{
	int x,y;
} Node;
bool cmp(const Node& a,const Node& b){
	if(a.x==b.x)
		return a.y<b.y;
	return a.x<b.x;
}
int N,ans,mx,my;
Node nodes[50000];
int main(){
	while(cin>>N&&N){
		for(int i=0;i<N;i++){
			cin>>nodes[i].x>>nodes[i].y;
		}
		sort(nodes,nodes+N,cmp);
		ans=1;
		mx=nodes[N-1].x;
		my=nodes[N-1].y;
		for(int i=N-2;i>=0;i--){
			if(nodes[i].x==mx)
				continue;
			if(nodes[i].y>my){
				mx=nodes[i].x;
				my=nodes[i].y;
				ans++;
			}
		}
		cout<<ans<<endl;
	}

	return 0;
}