#include <iostream>
#include <bits/stdc++.h>

using namespace std;

typedef struct
{
    int e;
    int v;
    bool volte=false;
}Interv;

/*
9
1 3
8 10
1 7
2 7
2 3
9 11
2 4
3 9
3 8
*/

bool eszerint(Interv i1, Interv i2)
{
    if(i1.e!=i2.e)
        return i1.e<i2.e;
    else
        return i1.v<i2.v;
}

void qkiir(queue<Interv> q)
{
    queue<Interv> seged=q;
    Interv v;
    while(!seged.empty())
    {
        v=seged.front();
        cout<<v.e<<". ."<<v.v<<" ";
        seged.pop();
    }
    cout<<endl;
}

int main()
{
    int n;
    cin>>n;
    vector<Interv> musor(n);

    for(int i=0;i<n;i++)
    {
        cin>>musor.at(i).e>>musor.at(i).v;
    }

    /*for(Interv x : musor)
        cout<<x.e<<"-"<<x.v<<" ";
    cout<<endl;*/

    sort(musor.begin(),musor.end(), eszerint);
    //cout<<endl;
    /*for(Interv x : musor)
        cout<<x.e<<"-"<<x.v<<endl;
    cout<<endl;*/


    queue<Interv> sor;
    Interv jelol;
    jelol.e=-1;
    jelol.v=-1;

    for(Interv x : musor)
    {
        sor.push(x);

    }
    sor.push(jelol);
    //qkiir(sor);

    /*while(sor.size()>1)
    {
        Interv most;
        most=sor.front();
        cout<<most.e<<"--"<<most.v<<" ";
        sor.pop();
        Interv uj=sor.front();
        while(most.v<uj.e && uj.e!=-1)
        {
            sor.push(uj);
            sor.pop();
            uj=sor.front();
            qkiir(sor);
        }
        if(most.v==uj.e)
        {
            cout<<uj.e<<"--"<<uj.v<<" ";
            most=uj;
            sor.pop();
            uj=sor.front();
            qkiir(sor);
        }
        else if (uj.e==-1)
        {
            sor.pop();
            sor.push(uj);
            //most=sor.front();
            qkiir(sor);
        }

    }*/

    //Interv seged;
    int szamol=0;
    while(sor.size()>1)
    {
        Interv most;
        most=sor.front();
        //cout<<most.e<<"--"<<most.v<<" ";
        sor.pop();
        //Interv uj=sor.front();
        //cout<<most.e<<" "<<most.v<<" --> ";
        while(sor.front().e!=-1)
        {
            if(most.v==sor.front().e)
            {
                most=sor.front();
                sor.pop();
                //cout<<most.e<<" "<<most.v<<" --> ";
            }
            else
            {
                sor.push(sor.front());
                sor.pop();

            }
        }
        //cout<<endl;
        szamol++;
        sor.push(sor.front());
        sor.pop();

    }
    cout<<szamol;


    return 0;
}