线段覆盖

// An highlighted block
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
using namespace std;
struct Node{
	int l, r, w;
}p[1000005];
int n, ll, rr, ww;
int dp[1000005];

bool cmp(Node a, Node b) {
	if (a.r < b.r) return true;
	if (a.r == b.r && a.l < b.l) return true;
	return false;
}

int findd(int x, int l, int r)
{
	while (l < r) {
		int mid = (r + l + 1) >> 1;
		if (p[mid].r <= x) l = mid;
		else r = mid - 1;
	}
	return l;
}



// 枚举 每一条线段 
int main()
{
	cin>>n;
	for (int i=1; i<=n; i++){
	//    cin>>ll>>rr>>ww;
	    cin>>ll>>rr; ww = 1;
	    if(ll > rr) swap(ll, rr);
		p[i].l = ll, p[i].r = rr, p[i].w = ww;	
	}
	sort(p+1, p+n+1, cmp); 
	p[0].l = -1000, p[0].r = -1000, p[0].w = 0;
    dp[0] = 0;
	for (int i=1; i<=n; i++){
        int k = findd(p[i].l, 0, i-1);
        dp[i] = max(dp[i-1], dp[k]+p[i].w);
	}
	cout<<dp[n]<<endl;
}                         



// 枚举坐标
struct Edge{
	int v, nex, w;
}e[1000005];
int tot, a[1000005], f[1000005];

void add(int from, int to, int val){
	e[++tot].v = to;
	e[tot].nex = a[from];
	e[tot].w = val;
	a[from] = tot;
}   

int main()
{
//	freopen("test.in", "r", stdin);
	cin>>n;
	int max_r = -1;
	for (int i=1; i<=n; i++){
		cin>>ll>>rr>>ww;
	//    cin>>ll>>rr; ww = 1;
		if(ll > rr) swap(ll, rr);
		add(rr, ll, ww);
		max_r = max(max_r, rr);	
	}
	f[0] = 0;
	for (int i=1; i<=max_r; i++){
		f[i] = f[i-1];
		for (int j=a[i]; j; j=e[j].nex)
		    f[i] = max(f[i], f[e[j].v]+e[j].w);
	}
	cout<< f[max_r] <<endl;
}