import java.util.*;
import java.io.*;
public class mobile {
private static double[][] info;
private static int l;
private static boolean check(double rad){
double max = 0;
for (int i = 0; i < info.length; i++) {
double[] intersect = intersect(info[i], rad);
if(intersect[0] <= max){
max = Math.max(max, intersect[1]);
}
}
return max >= l;
}
private static double[] intersect(double[] point, double rad){
double change = Math.sqrt(rad * rad - point[1] * point[1]);
return new double[]{point[0] - change, point[0] + change};
}
public static void main(String[] args) throws IOException{
FastIO io = new FastIO();
int n = io.nextInt(); l = io.nextInt();
info = new double[n][2];
for (int i = 0; i < n; i++) {
info[i][0] = io.nextInt(); info[i][1] = io.nextInt();
}
double left = 0; double right = l;
for (int i = 0; i < 100; i++) {
double mid = left + (right - left)/2;
if(check(mid)){
right = mid;
}
else{
left = mid;
}
}
io.println(left);
io.close();
}
}
class FastIO extends PrintWriter {
private InputStream stream;
private byte[] buf = new byte[1 << 16];
private int curChar;
private int numChars;
// standard input
public FastIO() { this(System.in, System.out); }
public FastIO(InputStream i, OutputStream o) {
super(o);
stream = i;
}
// file input
public FastIO(String i, String o) throws IOException {
super(new FileWriter(o));
stream = new FileInputStream(i);
}
// throws InputMismatchException() if previously detected end of file
private int nextByte() {
if (numChars == -1) { throw new InputMismatchException(); }
if (curChar >= numChars) {
curChar = 0;
try {
numChars = stream.read(buf);
} catch (IOException e) { throw new InputMismatchException(); }
if (numChars == -1) {
return -1; // end of file
}
}
return buf[curChar++];
}
// to read in entire lines, replace c <= ' '
// with a function that checks whether c is a line break
public String next() {
int c;
do { c = nextByte(); } while (c <= ' ');
StringBuilder res = new StringBuilder();
do {
res.appendCodePoint(c);
c = nextByte();
} while (c > ' ');
return res.toString();
}
public int nextInt() { // nextLong() would be implemented similarly
int c;
do { c = nextByte(); } while (c <= ' ');
int sgn = 1;
if (c == '-') {
sgn = -1;
c = nextByte();
}
int res = 0;
do {
if (c < '0' || c > '9') { throw new InputMismatchException(); }
res = 10 * res + c - '0';
c = nextByte();
} while (c > ' ');
return res * sgn;
}
public double nextDouble() { return Double.parseDouble(next()); }
}
