#include <stdio.h>
#include <algorithm>
using namespace std;

const int maxs = 500;
int c,g[1010][maxs*2+1],s[1010],p[1010],r[100010];

void just()
{
	int n = 0;
	for (int i=0;i<c;i++){
		for (int j=0;j<s[i];j++){
			r[n++] = g[i][j] + p[i];
		}
	}

	c = (n + maxs - 1) / maxs;
	for (int i=0;i<c;i++) s[i] = p[i] = 0;
	for (int i=0;i<n;i++){
		g[i/maxs][i%maxs] = r[i];
		s[i/maxs]++;
	}
}

void del(int i, int v)
{
	s[i]--;
	for (int j=v;j<s[i];j++) g[i][j] = g[i][j+1];
}

void rem(int y)
{
	for (int i=0;i<c;i++) if (s[i]){
		if (y <= g[i][s[i]-1] + p[i]){
			for (int v=0;v<s[i];v++){
				if (y <= g[i][v] + p[i]){
					del(i,v);
					if (s[i] == 0) just();
					return;
				}
			}
		}
	}
}

void add(int x, int y)
{
	for (int i=0;i<c;i++) if (s[i]){
		int a = g[i][0] + p[i];
		int b = g[i][s[i]-1] + p[i];
		if (x <= a && b <= y) p[i]++;
		else if (max(x,a) <= min(b,y)){
			for (int v=0;v<s[i];v++){
				int &a = g[i][v];
				a += p[i];
				if (x <= a && a <= y) a++;
			}
			p[i] = 0;
		}
	}
}

void mak(int i, int v)
{
	for (int j=s[i];j>v;j--) g[i][j] = g[i][j-1];
	s[i]++;
}

void ins(int x)
{
	if (c == 0){
		g[0][0] = x; s[0] = 1; p[0] = 0; c = 1;
		return;
	}

	for (int i=0;i<c;i++){
		if (x <= g[i][s[i]-1] + p[i] || i == c-1){
			int v = 0;
			while (v < s[i] && x > g[i][v] + p[i]) v++;
			mak(i,v);
			g[i][v] = x - p[i];
			if (s[i] == maxs*2) just();
			break;
		}
	}
}

int main()
{
	int N; scanf ("%d",&N); while (N--){
		int x,y; scanf ("%d %d",&x,&y);
		rem(y);
		add(x,y);
		ins(x);
	}

	int ans = 0;
	for (int i=0;i<c;i++) ans += s[i];
	printf ("%d\n",ans);

	return 0;
}