#include <algorithm>
#include <cstdio>

using namespace std;

struct Movie {
  int s;
  int e;
  bool operator<(const Movie that) const { return this->e < that.e; }
};

int main() {
  int n;
  Movie m[100];
  for (;;) {
    scanf("%d", &n);
    if (n == 0) break;
    for (int i = 0; i < n; i++) scanf("%d %d", &m[i].s, &m[i].e);
    sort(m, m + n);
    int pre = -1, cnt = 0;
    for (int i = 0; i < n; i++) {
      if (pre <= m[i].s) {
        cnt++;
        pre = m[i].e;
      }
    }
    printf("%d\n", cnt);
  }
  return 0;
}