#include <bits/stdc++.h>
using namespace std;
long long n,x,y,l,a[1000010],dp[1000010];
int main()
{
    cin>>n;
    memset(a,-0x3f,sizeof(a));
    for(long long i=1;i<=n;i++){
        cin>>x >>y;
        if(x>y) x^=y,y^=x,x^=y;
        x+=1000,y+=1000;
		l=max(l,y);
        if(x>a[y]) a[y]=x;
    }
    for(long long i=1;i<=l;i++){
        if(a[i]>=0) dp[i]=max(dp[i-1],dp[a[i]]+1);
        else dp[i]=dp[i-1];
    }
    cout<<dp[l] <<endl;
    return 0;
}

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