import java.awt.geom.Line2D;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Comparator;
import java.util.InputMismatchException;

public class Main {
	static InputStream is;
	static PrintWriter out;
	static String INPUT = "";
	
	static void solve()
	{
		int n = ni();
		if(n == 0){
			out.println(1);
			return;
		}
		int[][] co = new int[n][];
		long[] codes = new long[n];
		for(int i = 0;i < n;i++){
			co[i] = new int[]{ni(), ni()};
			codes[i] = co[i][0]+20000L<<48|co[i][1]+20000L<<32|i+1;
		}
		Arrays.sort(codes);
		int p = 0;
		for(int i = 0;i < n;i++){
			if(i == 0 || codes[i]>>>32 != codes[i-1]>>>32){
				codes[p++] = codes[i];
			}
		}
		codes = Arrays.copyOf(codes, p);
		
		DJSet ds = new DJSet(n);
		for(int i = 0;i < n;i++){
			int x = co[i][0], y = co[i][1];
			for(int j = -10;j <= 10;j++){
				for(int k = -10;k <= 10;k++){
					if(j*j+k*k <= 100){
						int dx = x + j, dy = y + k;
						long low = (long)dx+20000L<<48|dy+20000L<<32|0;
						int ind = Arrays.binarySearch(codes, low);
						ind = -ind-1;
						if(ind < codes.length && codes[ind]>>>32 == low>>>32){
							ds.union(((int)codes[ind])-1, i);
						}
					}
				}
			}
		}
		
		int[][] g = makeBuckets(ds);
		double max = 0;
		for(int[] row : g){
			int m = row.length;
			double[][] lco = new double[m][];
			for(int i = 0;i < m;i++){
				lco[i] = new double[]{co[row[i]][0], co[row[i]][1]};
			}
			double[][] hull = convexHull(lco);
			max = Math.max(max, findMostFarPair(hull) + 2);
		}
		out.printf("%.12f\n", max);
	}
	
	public static double findMostFarPair(double[][] co)
	{
		int h = co.length;
		if(h <= 1)return 0.;
		int is = 0, js = 0;
		for(int j = 1;j < h;j++){
			if(co[j][1] > co[is][1])is = j;
			if(co[j][1] < co[js][1])js = j;
		}
		double max = 
				(co[is][0]-co[js][0])*(co[is][0]-co[js][0])+
				(co[is][1]-co[js][1])*(co[is][1]-co[js][1]);
		
		int i, maxi, j, maxj;
		i = maxi = is;
		j = maxj = js;
		int ii = i+1, jj = j+1;
		if(ii >= h)ii -= h;
		if(jj >= h)jj -= h;
		do{
			double ax = co[ii][0]-co[i][0];
			double ay = co[ii][1]-co[i][1];
			double bx = co[jj][0]-co[j][0];
			double by = co[jj][1]-co[j][1];
			if(ax*by-ay*bx >= 0){
				j = jj;
				jj = j+1;
				if(jj >= h)jj -= h;
			}else{
				i = ii;
				ii = i+1;
				if(ii >= h)ii -= h;
			}
			double nor = 
					(co[i][0]-co[j][0])*(co[i][0]-co[j][0])+
					(co[i][1]-co[j][1])*(co[i][1]-co[j][1]);
			if(nor > max){
				max = nor;
				maxi = i;
				maxj = j;
			}
		}while(i != is || j != js);
		
		return Math.sqrt(max);
	}
	
	public static double[][] convexHull(double[][] co)
	{
		int n = co.length;
		if(n <= 1)return co;
		Arrays.sort(co, new Comparator<double[]>(){
			public int compare(double[] a, double[] b){
				if(a[0] - b[0] != 0)return (int)Math.signum(a[0] - b[0]);
				return (int)Math.signum(a[1] - b[1]);
			}
		});
		
		int[] inds = new int[n + 1];
		int p = 0;
		for(int i = 0;i < n;i++){
			if(p >= 1 && co[inds[p-1]][0] == co[i][0] && co[inds[p-1]][1] == co[i][1])continue;
			while(p >= 2 && Line2D.relativeCCW(
					co[inds[p-2]][0], co[inds[p-2]][1],
					co[inds[p-1]][0], co[inds[p-1]][1],
					co[i][0], co[i][1]) == 1)p--;
			inds[p++] = i;
		}
		
		int inf = p + 1;
		for(int i = n - 2;i >= 0;i--){
			if(co[inds[p-1]][0] == co[i][0] && co[inds[p-1]][1] == co[i][1])continue;
			while(p >= inf && Line2D.relativeCCW(
					co[inds[p-2]][0], co[inds[p-2]][1],
					co[inds[p-1]][0], co[inds[p-1]][1],
					co[i][0], co[i][1]) == 1)p--;
			inds[p++] = i;
		}
		
		double[][] ret = new double[p-1][];
		for(int i = 0;i < p-1;i++)ret[i] = co[inds[i]];
		return ret;
	}
	
	public static int[][] makeBuckets(DJSet ds)
	{
		int n = ds.upper.length;
		int[] roots = new int[n];
		int[] where = new int[n];
		int p = 0;
		for(int i = 0;i < n;i++){
			if(ds.upper[i] < 0){
				roots[p++] = i;
				where[i] = p-1;
			}
		}
		int[][] bucket = new int[p][];
		for(int i = 0;i < p;i++){
			bucket[i] = new int[-ds.upper[roots[i]]];
		}
		
		int[] bp = new int[p];
		for(int i = 0;i < n;i++){
			int ind = where[ds.root(i)];
			bucket[ind][bp[ind]++] = i;
		}
		return bucket;
	}
	
	public static class DJSet {
		public int[] upper;

		public DJSet(int n) {
			upper = new int[n];
			Arrays.fill(upper, -1);
		}

		public int root(int x) {
			return upper[x] < 0 ? x : (upper[x] = root(upper[x]));
		}

		public boolean equiv(int x, int y) {
			return root(x) == root(y);
		}

		public boolean union(int x, int y) {
			x = root(x);
			y = root(y);
			if (x != y) {
				if (upper[y] < upper[x]) {
					int d = x;
					x = y;
					y = d;
				}
				upper[x] += upper[y];
				upper[y] = x;
			}
			return x == y;
		}

		public int count() {
			int ct = 0;
			for (int u : upper)
				if (u < 0)
					ct++;
			return ct;
		}
	}
	
	public static void main(String[] args) throws Exception
	{
//		int n = 120000, m = 99999;
//		Random gen = new Random();
//		StringBuilder sb = new StringBuilder();
//		sb.append(n + " ");
//		for (int i = 0; i < n; i++) {
//			sb.append(gen.nextInt(20000)-10000 + " ");
//			sb.append(gen.nextInt(20000)-10000 + " ");
//		}
//		INPUT = sb.toString();
		
		long S = System.currentTimeMillis();
		is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		solve();
		out.flush();
		long G = System.currentTimeMillis();
		tr(G-S+"ms");
	}
	
	private static boolean eof()
	{
		if(lenbuf == -1)return true;
		int lptr = ptrbuf;
		while(lptr < lenbuf)if(!isSpaceChar(inbuf[lptr++]))return false;
		
		try {
			is.mark(1000);
			while(true){
				int b = is.read();
				if(b == -1){
					is.reset();
					return true;
				}else if(!isSpaceChar(b)){
					is.reset();
					return false;
				}
			}
		} catch (IOException e) {
			return true;
		}
	}
	
	private static byte[] inbuf = new byte[1024];
	static int lenbuf = 0, ptrbuf = 0;
	
	private static int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private static boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private static int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private static double nd() { return Double.parseDouble(ns()); }
	private static char nc() { return (char)skip(); }
	
	private static String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private static char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private static char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private static int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private static int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private static void tr(Object... o) { if(INPUT.length() != 0)System.out.println(Arrays.deepToString(o)); }
}