#include<bits/stdc++.h> #define range(i,a,b) for(int i=a;i<=b;++i) #define LL long long #define rerange(i,a,b) for(int i=a;i>=b;--i) #define fill(arr,tmp) memset(arr,tmp,sizeof(arr)) using namespace std; pair<int,int>aa[115]; int n,ans,tag; void init(){ } void swap(int&a,int&b){ int tmp=a; a=b; b=tmp; } bool cmp(pair<int,int>a,pair<int,int>b){ return a.second<b.second; } void solve(){ while(cin>>n,n){ int s,e; range(i,1,n){ cin>>s>>e; if(s>e)swap(s,e); aa[i].first=s; aa[i].second=e; } sort(aa+1,aa+1+n,cmp); tag=ans=0; range(i,1,n) if(aa[i].first>=tag){ ++ans; tag=aa[i].second; } cout<<ans<<endl; } } int main() { init(); solve(); return 0; }