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

struct vedio
{
    int l,r;
}a[1005];
int n;

bool cmp(vedio x,vedio y)
{
    return x.r < y.r;
}

int main()
{
    while(scanf("%d",&n) && n)
    {
        for(int i = 1;i <= n;i++)    scanf("%d%d",&a[i].l,&a[i].r);
        sort(a+1,a+1+n,cmp);
        int ans = 1,time = a[1].r,now = 2;
        for(;now <= n;now++)
        {
            if(time > a[now].l)    continue;
            time = a[now].r;
            ans++;
        }
        printf("%d\n",ans);
    }
    return 0;
}