#include <bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
using namespace std;

#define maxn 2000005
#define inf 0x3f3f3f3f
#define pb push_back
typedef vector<int>vi;

int n,x[maxn],y[maxn];

int tmpx[maxn],tmpy[maxn],nx,ny;
void workx(int ds[]) {sort(ds+1,ds+ds[0]+1);ds[0]=unique(ds+1,ds+ds[0]+1)-ds-1;}

int l[maxn],r[maxn];

int f[maxn],g[maxn];

int mxl[20][maxn],mnr[20][maxn];
int qmaxl(int l,int r){
    int k=__lg(r-l+1);
    return max(mxl[k][l],mxl[k][r-(1<<k)+1]);
}
int qminr(int l,int r){
    int k=__lg(r-l+1);
    return min(mnr[k][l],mnr[k][r-(1<<k)+1]);
}

int nxt[maxn];

struct segt{
    int tag[maxn<<2],mn[maxn<<2];
    void init(){
        memset(mn,63,sizeof mn);
        memset(tag,63,sizeof tag);
    }
    int ask(int p,int l,int r,int ql,int qr){
        if(ql>qr)return inf;
        if(l>=ql && r<=qr) return mn[p];
        //cout<<"ask "<<p<<" "<<l<<" "<<r<<"\n";
        int mid=l+r>>1,res=tag[p];
        if(ql<=mid)res=min(res,ask(p<<1,l,mid,ql,qr));
        if(qr>mid)res=min(res,ask(p<<1|1,mid+1,r,ql,qr));
        return res;
    }
    void mdf(int p,int l,int r,int ql,int qr,int t){
        if(ql>qr)return;
        if(l>=ql&&r<=qr){
            tag[p]=min(tag[p],t);
            mn[p]=min(mn[p],t);
            return;
        }
        int mid=l+r>>1;
        if(ql<=mid)mdf(p<<1,l,mid,ql,qr,t);
        if(qr>mid)mdf(p<<1|1,mid+1,r,ql,qr,t);
        mn[p]=min(min(tag[p],mn[p<<1]),mn[p<<1|1]);
    }
    int ask(int ql,int qr){
        return ask(1,1,nx,ql,qr);
    }
    void mdf(int ql,int qr,int v){
        mdf(1,1,nx,ql,qr,v);
    }
}F,G;


int pre1[maxn],pre2[maxn],pre3[maxn],pre4[maxn];
int l2[maxn],r2[maxn];

int main()
{
    cin>>n;
    For(i,1,n)cin>>x[i]>>y[i];
    
    tmpx[0]=0; For(i,1,n)tmpx[++tmpx[0]]=x[i];
    workx(tmpx); nx=tmpx[0];
    For(i,1,n)x[i]=lower_bound(tmpx+1,tmpx+tmpx[0]+1,x[i])-tmpx;

    tmpy[0]=0; For(i,1,n)tmpy[++tmpy[0]]=y[i];
    workx(tmpy); ny=tmpy[0];
    For(i,1,n)y[i]=lower_bound(tmpy+1,tmpy+tmpy[0]+1,y[i])-tmpy;

    For(i,1,nx) l[i]=-1,r[i]=inf;
    For(i,1,n) {
        int j=i+1; if(j>n) j=1;
        if(y[i]!=y[j]){
            
        }else{
            if(x[i]<x[j]){
                For(k,x[i],x[j]-1) l[k]=max(l[k],y[i]);
            }else{
                For(k,x[j],x[i]-1) r[k]=min(r[k],y[i]);
            }
        }
    }
    For(i,1,nx) --r[i];
    --nx;

  /*  For(i,1,nx){
       cout<<"l,r "<<l[i]<<" "<<r[i]<<"\n";
    }
 cout<<"-----\n";*/

    /*int nx2=0;
    For(i,1,nx) {
        l2[++nx2]=l[i],r2[nx2]=r[i];
        if(i==nx) continue;
        l2[++nx2]=min(l[i],l[i+1]);
        r2[nx2]=max(r[i],r[i+1]);
    }
    nx=nx2;
    For(i,1,nx) l[i]=l2[i],r[i]=r2[i];
    */

  /* For(i,1,nx){
       cout<<"l,r "<<l[i]<<" "<<r[i]<<"\n";
    }
 cout<<"-----\n";*/

    For(i,1,nx){
        mxl[0][i]=l[i];
        mnr[0][i]=r[i];
    }
    For(j,1,19){
        For(i,1,nx-(1<<j)+1){
            mxl[j][i]=max(mxl[j-1][i],mxl[j-1][i+(1<<(j-1))]);
            mnr[j][i]=min(mnr[j-1][i],mnr[j-1][i+(1<<(j-1))]);
        }
    }

    int res=inf;
    f[0]=g[0]=0;
    For(i,1,nx) f[i]=g[i]=inf;

    int pre=0;

    nxt[nx]=nx+1;
    Rep(i,nx-1,0){
        if(l[i]>l[i+1] || r[i]<r[i+1]) nxt[i]=i;
        else nxt[i]=nxt[i+1];
    }

    For(i,2,nx){
        pre1[i]=pre1[i-1],pre2[i]=pre2[i-1];
        pre3[i]=pre3[i-1],pre4[i]=pre4[i-1];
        if(r[i-1]<r[i]) pre1[i]=i;
        if(r[i-1]>r[i]) pre2[i]=i;
        if(l[i-1]<l[i]) pre3[i]=i;
        if(l[i-1]>l[i]) pre4[i]=i;
    }

    F.init(),G.init();

    int nl=l[1],nr=r[1];
    For(i,1,nx){
        nl=max(nl,l[i]);
        nr=min(nr,r[i]);
        if(nl<=nr) G.mdf(i,i,1);
    }

    For(i,1,nx){
     //   cout<<"i: "<<i<<" "<<l[i]<<" "<<r[i]<<"\n";
        int ps=0,ql=1,qr=i-1;
        while(ql<=qr){
            int mid=ql+qr>>1;
            if(qmaxl(mid,i) <= qminr(mid,i)+1) qr=mid-1;
            else ps=mid,ql=mid+1;//cout<<"Qmaxl,minr "<<mid<<" "<<i<<" "<<qmaxl(mid,i)<<" "<<qminr(mid,i)<<"\n";
        }++ps;

        {
            int u=pre1[pre2[i]];
         //   cout<<"R[u] "<<i<<" "<<u<<"\n";
            ps=max(ps,u);
            u=pre4[pre3[i]];
        //    cout<<"L[u] "<<i<<" "<<u<<"\n";
            ps=max(ps,u);
         //   cout<<"ps "<<ps<<"\n";
        }

      /*  Rep(j,i-1,ps){
            f[i]=min(f[i],f[j]+1);
        }*/

        int val=F.ask(ps,i-1)+1; 
        F.mdf(i,i,val);

        if(l[i-1]<l[i] || r[i-1]>r[i]) pre=i-1;

        int id=pre;
        if(!id) F.mdf(i,i,1);
        else {
            int val=G.ask(id,i-1)+1;
            F.mdf(i,i,val);
        }

        
        ps=nxt[i];
         val=F.ask(i,i);
        G.mdf(i+1,ps,val);
       // For(j,i+1,ps) g[j]=min(g[j],f[i]);

       /* For(j,i+1,nx){
            if(l[j-1]>l[j] || r[j-1]<r[j]) {
                break;
            }
            g[j]=min(g[j],f[i]);
        }*/
        

        ql=i+1,qr=nx,ps=nx+1;
        while(ql<=qr){
            int mid=ql+qr>>1;
            if(qmaxl(i+1,mid) <= qminr(i+1,mid)) ql=mid+1;
            else qr=mid-1,ps=mid;
        } --ps;

         val=G.ask(i,i)+1;
         G.mdf(i+1,ps,val);
      //  For(j,i+1,ps) g[j]=min(g[j],g[i]+1);

        /*int L=l[i],R=r[i];
        For(j,i+1,nx){
            L=max(L,l[j]),R=min(R,r[j]);
            if(L<=R) g[j]=min(g[j],g[i]+1);
            else break;
        }*/
     //   cout<<"i: "<<i<<" "<<F.ask(i,i)<<" "<<G.ask(i,i)<<"\n";
    }
    cout<<min(F.ask(nx,nx),G.ask(nx,nx));
    return 0;
}
/*

*/