#include<stdio.h>
int main(){
	int h[1000],w[1000],a,b,j,i,n,T,m;
	scanf("%d",&T);
	n=T;
	i=1;
	while(T--){
		if(T==n-1){
			scanf("%d%d",&a,&b);
			h[0]=a;
			w[0]=b;
		}
		else{
			scanf("%d%d",&a,&b);
			for(j=0;j<i;j++){
				if((a<=h[j]&&b<=w[j])||(a<=w[j]&&b<=h[j])){
					h[j]=a;
					w[j]=b;
					break;
				}
			}
			if(j==i){
				i++;
				h[i-1]=a;
				w[i-1]=b;
			}
		}
	}
	printf("%d",i);
	return 0;
}