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

#define int long long

const int N=1e5+1e3+7;
const int inf=0x3f3f3f3f;

int n,m,l[N],r[N];

int il[N],ir[N],dl[N],dr[N];

struct P{
    int x,y;
}p[N];

int mxl[N][21],mnr[N][21];

int qmxl(int l,int r)
{
    int k=__lg(r-l+1);
    return max(mxl[l][k],mxl[r-(1<<k)+1][k]);
}

int qmnr(int l,int r)
{
    int k=__lg(r-l+1);
    return min(mnr[l][k],mnr[r-(1<<k)+1][k]);
}

int a[N],b[N],c[N];

int gl[N],gr[N];
int f[N],g[N];

int qlp(int x,int w)//[x...n], l[i]>w min(i)
{
    int l=x-1,r=n+1;
    while(r-l>1)
    {
        int mid=(l+r)>>1;
        if(qmxl(x,mid)>w)
            r=mid;
        else
            l=mid;
    }
    return r;
}

int qrp(int x,int w)//[x..n] r[i]<w min(i)
{
    int l=x-1,r=n+1;
    while(r-l>1)
    {
        int mid=(l+r)>>1;
        if(qmnr(x,mid)<w)
            r=mid;
        else
            l=mid;
    }
    return r;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n;
    vector<int> V;
    for(int i=1;i<=n;i++)
    {
        cin>>p[i].x>>p[i].y;
        V.push_back(p[i].y);
    }
    sort(V.begin(),V.end());
    for(int i=1;i<=n;i++)
        p[i].y=lower_bound(V.begin(),V.end(),p[i].y)-V.begin()+1;
    map<int,vector<int> >v;
    for(int i=1;i<=n;i++)
    {
        int j=i<n?i+1:1;
        if(p[i].y==p[j].y)
        {
            int L=min(p[i].x,p[j].x),R=max(p[i].x,p[j].x);
            v[L].push_back(p[i].y);
            v[R].push_back(-p[i].y);
        }
        else
            continue;
    }
    multiset<int> ms;
    m=0;
    for(auto [x,ys]:v)
    {
        for(auto y:ys)
            if(y>0)
                ms.insert(y);
        for(auto y:ys)
            if(y<0)
                ms.erase(ms.find(-y));
        assert(ms.size()==2||ms.size()==0);
        if(!ms.size())
            break;
        ++m;
        l[m]=*ms.begin();
        r[m]=*(next(ms.begin()));
    }
    // cout<<endl;
    // for(int i=1;i<=m;i++)
    //     cout<<l[i]<<" "<<r[i]<<endl;
    //end of prelude
    n=m;
    for(int i=1;i<=n;i++)
        mxl[i][0]=l[i],mnr[i][0]=r[i];
    for(int j=1;j<=20;j++)
        for(int i=1;i+(1<<j)-1<=n;i++)
        {
            mxl[i][j]=max(mxl[i][j-1],mxl[i+(1<<(j-1))][j-1]);
            mnr[i][j]=min(mnr[i][j-1],mnr[i+(1<<(j-1))][j-1]);
        }
    for(int i=1;i<=n;i++)
    {
        int l=i,r=n+1;
        while(r-l>1)
        {
            int mid=(l+r)>>1;
            if(qmxl(i,mid)<qmnr(i,mid))
                l=mid;
            else
                r=mid;
        }
        a[i]=l;
    }
    il[n]=dr[n]=b[n]=n;
    for(int i=n-1;i>=1;i--)
    {
        il[i]=(l[i]<=l[i+1]?il[i+1]:i);
        dr[i]=(r[i]>=r[i+1]?dr[i+1]:i);
        b[i]=min(il[i],dr[i]);
    }
    dl[n]=ir[n]=c[n]=n;
    for(int i=n-1;i>=1;i--)
    {
        dl[i]=(l[i]>=l[i+1]?dl[i+1]:i);
        ir[i]=(r[i]<=r[i+1]?ir[i+1]:i);
        c[i]=min(dl[i],ir[i]);
    }

    l[n+1]=1e9,r[n+1]=-1e9;

    #define ckmin(x,y) (x)=min((x),(y))
    memset(f,0x3f,sizeof(f));
    memset(g,0x3f,sizeof(g));
    int ans=inf;
    f[0]=0;
    // for(int i=1;i<=n;++i){
    //     cerr<<" i: "<<i<<" "<<l[i]<<' '<<r[i]<<" a: "<<a[i]<<" b: "<<b[i]<<" c: "<<c[i]<<endl;
    // }
    for(int i=0;i<=n;++i){
        if(i==n){
            ans=min(ans,f[i]);
            ans=min(ans,g[i]);
            break;
        }
        if(b[i]==n){
            ans=min(ans,g[i]);
        }
        else{
            ckmin(f[a[b[i]+1]],g[i]+1);
            if(b[i]+1==n){
                ans=min(ans,g[i]+1);
            }
            else{
                //no
                int L,R;
                if(l[b[i]+1]<l[b[i]]&&r[b[i]+1]>r[b[i]]){
                    L=l[b[i]+1];
                    R=r[b[i]+1];
                    if(!(l[b[i]+2]<=L&&r[b[i]+2]>=R)){
                        ckmin(g[b[i]+1],g[i]+1);
                    }
                    else{
                        ckmin(g[c[b[i]+2]],g[i]+1);
                    }
                }
                else if(r[b[i]+1]>r[b[i]]){
                    int z=n;
                    z=min(z,ir[b[i]+1]);
                    z=min(z,qlp(b[i]+1,r[b[i]])-1);
                    z=min(z,c[min(n,il[b[i]+1]+1)]);
                    ckmin(g[z],g[i]+1);
                    // if(i==3){
                    //     cerr<<" z: "<<z<<" "<<ir[b[i]+1]<<" "<<qlp(b[i]+1,r[b[i]])-1<<" "<<c[min(n,il[b[i]+1]+1)]<<endl;
                    // }
                }
                else{
                    int z=n;
                    z=min(z,dl[b[i]+1]);
                    z=min(z,qrp(b[i]+1,l[b[i]])-1);
                    z=min(z,c[min(n,dr[b[i]+1]+1)]);
                    ckmin(g[z],g[i]+1);
                }
            }
        }
        ckmin(f[a[i+1]],f[i]+1);
        ckmin(g[c[i+1]],f[i]+1);
    }
    ans=min(ans,f[n+1]);
    ans=min(ans,g[n+1]);
    ans=max(ans,1ll);
    cout<<ans<<'\n';
    return 0;
}