#include<bits/stdc++.h>

using namespace std;

int x,y,n,b[],ans,a[][],del[];

void getans()

{

    memset(del,,sizeof(del));

    int t=;

    for (int i=;i<=n;i++)

     if (!del[i])

      {

        t++;

        for (int j=i+;j<=n;j++)

         if (!a[b[i]][b[j]])del[j]=;

      }

    ans=max(t,ans);

}

int main()

{

    scanf("%d",&n);

    while (~scanf("%d%d",&x,&y))a[x][y]=a[y][x]=;

    for (int i=;i<=n;i++)b[i]=i;

    for (int i=;i<=;i++)

     {

        for (int j=;j<=n;j++)swap(b[j],b[rand()%j+]);

        getans();

     }

    printf("%d",ans);

    return ;

}