#include<stdio.h>
int main() {
	int n,i,t,p;
	int x=1;
	scanf("%d",&n);
	int h[n],w[n];
	int h1[n],w1[n];
	scanf("%d%d",&h[0],&w[0]);
	h1[0]=h[0];
	w1[0]=w[0];
	for(i=1; i<n; ++i) {
		scanf("%d%d",&h[i],&w[i]);
		if(h[i]<=h1[0]&&w[i]<=w1[0]) {
			h1[0]=h[i];
			w1[0]=w[i];
			continue;
		} else if(h[i]<=w1[0]&&w[i]<=h1[0]) {
			h1[0]=w[i];
			w1[0]=h[i];
			continue;
		} else {
			int p=0;
			for(t=0; t<x; ++t) {
				if(h[i]<=h1[t]&&w[i]<=w1[t]) {
					h1[t]=h[i];
					w1[t]=w[i];
					p=1;
					break;
				} else if(h[i]<=w1[t]&&w[i]<=h1[t]) {
					h1[t]=w[i];
					w1[t]=h[i];
					p=1;
					break;
				}
			}
			if(p==0) {
				h1[x]=h[i];
				w1[x]=w[i];
				++x;
			}
		}
	}
	printf("%d",x);
	return 0;
}