#include <cstdio>

#include <iostream>

#include <algorithm>

#include <cstdlib>

#include <cstring>

#include <queue>

#define N 100100

#define M 2000100

using namespace std;

struct sss

{

    int num;

    int du;

};

int n, m;

int p[N] = {}, next[M], v[M], bnum = ;

int du[N] = {}, vis[N] = {}, qu[N];

priority_queue<sss> q;

int hcolor[N] = {}, color[N] = {}, colornum = , huse[N] = {};

bool operator < (sss x, sss y)

{

    return x.du < y.du;

}

void addbian(int x, int y)

{

    bnum++; next[bnum] = p[x]; p[x] = bnum; v[bnum] = y;

    bnum++; next[bnum] = p[y]; p[y] = bnum; v[bnum] = x;

}

void make_queue()

{

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

    {

        sss x; x.num = i; x.du = ;

        q.push(x);

    }

    int dc = ;

    while (dc < n)

    {

        sss y = q.top(); q.pop();

        while (vis[y.num])

        {

            y = q.top();

            q.pop();

        }

        vis[y.num] = ;

        qu[++dc] = y.num;

        int k = p[y.num]; sss ne;

        while (k)

        {

            if (!vis[v[k]])

            {

                du[v[k]]++; ne.du = du[v[k]];

                ne.num = v[k]; q.push(ne);

            }

            k = next[k];

        }

    }

}

void color_dian()

{

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

    {

        int x = qu[i];

        int k = p[x];

        int all = ;

        while (k)

        {

            if (color[v[k]] != ) all = ;

            huse[color[v[k]]] = x;

            k = next[k];

        }

        int pd = ;

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

            if (huse[i] != x)

            {

                pd = ;

                color[x] = i;

                break;

            }

        if (!pd) color[x] = ++colornum;

    }

    printf("%d\n", colornum);

}

int main()

{

    scanf("%d%d", &n, &m);

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

    {

        int x, y; scanf("%d%d", &x, &y);

        addbian(x, y);

    }

    make_queue();

    color_dian();

    return ;

}