#include <bits/stdc++.h>

using namespace std;
typedef pair<int, int> PII;
#define x first
#define y second

const int N = 5010;
PII a[N];     // 南岸和北岸的一对友好城市的坐标
int f[N], fl; // 数组模拟栈
int n;        // n组友好城市
int res;

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i].x >> a[i].y;
    sort(a + 1, a + 1 + n);

    f[++fl] = a[1].y;
    for (int i = 2; i <= n; i++) {
        if (a[i].y > f[fl])
            f[++fl] = a[i].y;
        else
            *lower_bound(f + 1, f + 1 + fl, a[i].y) = a[i].y;
    }

    printf("%d\n", fl);
    return 0;
}