#include<bits/stdc++.h> using namespace std; struct TV{ int si,ei; }b[1010]; bool cmp(TV x,TV y){ return x.ei<y.ei; } int main(){ int n; while(1){ cin>>n; if(n==0){ return 0; } for(int i=1;i<=n;i++){ cin>>b[i].si>>b[i].ei; } sort(b+1,b+n+1,cmp); int end=b[1].ei; int cnt=1; for(int i=2;i<=n;i++){ if(b[i].si>=end){ cnt++; end=b[i].ei; } } cout<<cnt<<endl; } return 0; }