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> 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(); } }