#include <bits/stdc++.h>
using namespace std;

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)

#define bg begin()
#define ed end()
#define all(x) x.bg,x.ed
#define pb push_back
#define eb emplace_back
#define si(x) int(x.size())
template<class t>using vc=vector<t>;
template<class t>using vvc=vc<vc<t>>;
using vi=vc<int>;

#define a first
#define b second
#define mp make_pair
using pi=pair<int,int>;

template<class t,class u>bool chmin(t&a,u b){
	if(a>b){
		a=b;
		return true;
	}else return false;
}
template<class t,class u>bool chmax(t&a,u b){
	if(a<b){
		a=b;
		return true;
	}else return false;
}

template<class t>void mkuni(vc<t>&vs){
	sort(all(vs));
	vs.erase(unique(all(vs)),vs.ed);
}

template<class t>int lwb(const vc<t>&vs,t v){
	return lower_bound(all(vs),v)-vs.bg;
}

const int inf=INT_MAX/2-100;

template<class t,class u>
struct slide{
	vc<t> x;
	vi y;
	u f;
	int b,e,c,d;
	slide(u ff=u()):f(ff){init();}
	void init(){b=e=c=d=0;}
	void push(t a){
		while(b<e&&f(x[e-1],a))e--;
		if(e==si(x)){
			x.eb();
			y.eb();
		}
		x[e]=a;
		y[e++]=c++;
	}
	void pop(){if(y[b]==d)b++;d++;}
	t get(){return x[b];}
	bool has(){return b<e;}
};

void slv(){
	int n;cin>>n;
	vc<pi> xy(n);
	vi xs(n);
	rep(i,n){
		cin>>xy[i].a>>xy[i].b;
		xs[i]=xy[i].a;
	}
	mkuni(xs);
	
	vc<pi> lu(si(xs)-1);
	rep(i,n){
		auto [a,b]=xy[i];
		auto [c,d]=xy[(i+1)%n];
		a=lwb(xs,a);
		c=lwb(xs,c);
		if(a<c){
			rng(j,a,c)lu[j].a=b;
		}else if(a>c){
			rng(j,c,a)lu[j].b=b;
		}
	}
	lu.erase(unique(all(lu)),lu.ed);
	int s=si(lu);
	
	vvc<pi> g(2*(s+1));
	rep(k,2)rep(i,s)g[(i+1)*2+k].eb(i*2+k,0);
	rep(i,s+1)g[i*2].eb(i*2+1,0);
	{
		vi special(s+1);iota(all(special),0);
		rep(_,2){
			int tail=s;
			per(head,s){
				if(head+2<=tail&&lu[head].a<=lu[head+1].a&&lu[head].b<=lu[head+1].b){
					while(lu[head].b<lu[tail-1].a)tail--;
				}else tail=head+1;
				if(head+2<=tail)chmax(special[head+1],tail-1);
			}
			rep(i,s){
				swap(lu[i].a,lu[i].b);
				lu[i].a*=-1;
				lu[i].b*=-1;
			}
		}
		
		vi lf(s);
		rep(i,s){
			if(i>0&&lu[i].a<=lu[i-1].a&&lu[i-1].b<=lu[i].b)
				lf[i]=lf[i-1];
			else
				lf[i]=i;
		}
		vi rt(s);
		per(i,s){
			if(i+1<s&&lu[i].a<=lu[i+1].a&&lu[i+1].b<=lu[i].b)
				rt[i]=rt[i+1];
			else
				rt[i]=i+1;
		}
		
		rep(i,s){
			int x=lf[i],y=rt[i];
			g[x*2+1].eb(y*2,1);
			g[x*2+1].eb(special[y]*2+1,1);
		}
	}
	{
		slide<int,less<int>> l;
		slide<int,greater<int>> r;
		int j=0;
		rep(i,s){
			l.push(lu[i].a);
			r.push(lu[i].b);
			while(l.get()>=r.get()){
				l.pop();
				r.pop();
				j++;
			}
			
			int x=j,y=i+1;
			g[x*2].eb(y*2,1);
		}
	}
	
	vi dist(si(g),inf);
	deque<int> q;
	auto reach=[&](int v,int d,bool f){
		if(chmin(dist[v],d)){
			if(f)q.push_front(v);
			else q.push_back(v);
		}
	};
	reach(0,0,true);
	while(si(q)){
		int v=q.front();q.pop_front();
		for(auto [to,c]:g[v])reach(to,dist[v]+c,c==0);
	}
	cout<<dist[s*2]<<endl;
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	slv();
}