#include <stdio.h>
#include <algorithm>
using namespace std;
#define PLINE printf("\n------------------\n")
struct time
{
int s,e;
}t[101];
int n, ans;
bool cmp(struct time a, struct time b)
{
return a.s < b.s;
}
void search(int d, int num, int e)
{
if(d == n)//刚开始竟然把层数写错了,╮(╯▽╰)╭,以后还是搞统一吧
{
if(num > ans)
ans = num;
return;
}
if(t[d].s >= e)
search(d+1, num+1, t[d].e);
search(d+1, num, e);
}
int main()
{
int i;
while(scanf("%d", &n) && n )
{
ans = 0;
for(i=0; i<n; i++)
scanf("%d%d", &t[i].s, &t[i].e);
sort(t, t+n, cmp);
search(0, 0, 0);
printf("%d\n", ans);
}
return 0;
}
//贪心解法
include <stdio.h>
#include <algorithm>
using namespace std;
#define PLINE printf("\n------------------\n")
struct time
{
int s,e;
}t[101];
bool cmp(struct time a, struct time b)
{
return a.e < b.e;
}
int main()
{
int i, n, ans, e;
while(scanf("%d", &n) && n )
{
ans = 0;
for(i=0; i<n; i++)
scanf("%d%d", &t[i].s, &t[i].e);
sort(t, t+n, cmp);
e = 0;
for(i=0; i<n; i++)
if(t[i].s >= e)
{
e = t[i].e;
ans++;
}
printf("%d\n", ans);
}
return 0;
}