#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

struct VideoNode {
    int begin;
    int end;
};

struct VideoNode video[1001];

int cmp(struct VideoNode v1,struct VideoNode v2){
    return (v1.end < v2.end);
}

int main(){
    int n;
    while (scanf("%d",&n) != EOF){
        if (n == 0) break; 
        int i;
        for (i=0;i<n;i++){
            int begin,end;
            scanf("%d %d",&begin,&end);
            video[i].begin = begin;
            video[i].end = end;
        } 
        sort(video,video+n,cmp);
        int total = 0,time = -1;
        for (i=0;i<n;i++){
            if (video[i].begin >= time){
                time = video[i].end; 
                total ++;
            }
        }
        printf("%d\n",total);
    }
    return 0;
}