import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;

public class Main implements Runnable {
	public static void main(String[] args) {
		new Thread(null, new Main(), "", Runtime.getRuntime().maxMemory()).start();
	}
	
	class DSU {
		int[] parent;
		public DSU(int n) {
			parent=new int[n];
			Arrays.fill(parent, -1);
		}
		boolean isRoot(int x) {
			return parent[x]<0;
		}
		int root(int x) {
			return isRoot(x) ? x : (parent[x]=root(parent[x]));
		}
		boolean equiv(int x, int y) {
			return root(x)==root(y);
		}
		void union(int x, int y) {
			x=root(x);
			y=root(y);
			if (x==y) return;
			parent[y]+=parent[x];
			parent[x]=y;
		}
		int sz(int x) {
			return -parent[root(x)];
		}
	}
	
	public void run() {
		FastScanner sc = new FastScanner();
		PrintWriter pw=new PrintWriter(System.out);
		
		int N=sc.nextInt();
		int M=sc.nextInt();
		
		if (!(2 <= N && N <= 2e5)) throw new AssertionError();
		if (!(N-1 <= M && M <= Math.min(1L*N*(N-1)/2, 2e5))) throw new AssertionError();
		
		int[] u=new int[M];
		int[] v=new int[M];
		for (int i=0;i<M;++i) {
			u[i]=sc.nextInt();
			v[i]=sc.nextInt();
			if (!(1 <= u[i] && u[i] < v[i] && v[i] <= N)) throw new AssertionError();
			--u[i];--v[i];
		}
		Set<List<Integer>> set=new HashSet<>();
		DSU dsu=new DSU(N);
		int[] ans=new int[N];
		Arrays.fill(ans, 0);
		for (int i=M-1;i>=0;--i) {
			int nv=Math.max(ans[dsu.root(u[i])], ans[dsu.root(v[i])])+1;
			dsu.union(u[i], v[i]);
			ans[dsu.root(u[i])]=nv;
			if (set.contains(List.of(u[i],v[i]))) throw new AssertionError();
			set.add(List.of(u[i],v[i]));
		}
		if (dsu.sz(0)!=N) throw new AssertionError();
		System.out.println(Arrays.stream(ans).max().getAsInt());
		pw.close();
	}

	void tr(Object... objects) {
		System.err.println(Arrays.deepToString(objects));
	}
}

class FastScanner {
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;

	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}

	private int readByte() {
		if (hasNextByte())
			return buffer[ptr++];
		else
			return -1;
	}

	private static boolean isPrintableChar(int c) {
		return 33 <= c && c <= 126;
	}

	private void skipUnprintable() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
	}

	public boolean hasNext() {
		skipUnprintable();
		return hasNextByte();
	}

	public String next() {
		if (!hasNext())
			throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while (isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	public long nextLong() {
		if (!hasNext())
			throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while (true) {
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			} else if (b == -1 || !isPrintableChar(b)) {
				return minus ? -n : n;
			} else {
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}

	public int nextInt() {
		return (int) nextLong();
	}
}