#include <cstdio>
#include <algorithm>
using namespace std;
const int N = 5000 + 10;
struct mugun {
    int l, w;
    inline bool operator < (const mugun x) const {
        return l == x.l ? w < x.w : l < x.l;
    }
} a[N];
int n, f[N];
int main() {
    freopen("wooden.in", "r", stdin);
    freopen("wooden.out", "w", stdout);
    scanf("%d", &n);
    for(int i=1; i<=n; i++)
        scanf("%d %d", &a[i].l, &a[i].w);
    for(int i=1; i<=n; i++)
        f[i] = 1;
    sort(a+1, a+n+1);
    for(int i=1; i<=n; i++)
        for(int j=1; j<i; j++)
            if(a[j].w > a[i].w && f[i] <= f[j])
                f[i] = f[j] + 1;
    printf("%d\n", *max_element(f+1, f+n+1));
    return 0;
}