#include <iostream>

#include <algorithm>

struct ss{

    int a;

    int b;

}q[1000];

int ww (ss x, ss y){

    if(x.b < y.b)

        return 1;

    else

        if(x.b == y.b)

            if(x.a < y.a)

                return 1;

            else

                return 0;

        else

            return 0;

}

using namespace std;

int main(){

    int n, i, k, t;

    while(scanf("%d", &n) && (n != 0)){

        for(i =  0; i < n; i++){

            scanf("%d%d", &q[i].a, &q[i].b);

        }

        sort(q, q + n, ww);

        t = q[0].b;

        for(i = 1, k = 1; i < n; i++){

            if(t <= q[i].a){

                t = q[i].b;

                k++;}

        }

        printf("%d\n", k);

    }

    return 0;

}