/* Ms. Wear's Java Solution to CCC 2020 S1 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.*;

public class Main {
	public static void main(String[] args)  throws IOException {
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
 
        // Reading number of observations
        int n = Integer.parseInt(reader.readLine());
        
        Observation [] observations = new Observation[n];
        
        // read all observations
        for (int i = 0; i < observations.length; i++) {
        	String [] input = reader.readLine().split(" ");
        	int time = Integer.parseInt(input[0]);
        	int position = Integer.parseInt(input[1]);
        	observations[i] = new Observation(time, position);
        }
        
        Arrays.sort(observations);
        
        double maxSpeed = 0;
        
        for (int i = 1; i < observations.length; i++) {
        	double deltaTime = observations[i].time - observations[i-1].time;
        	double distance = Math.abs(observations[i].position - observations[i-1].position);
        	double speed  = distance/deltaTime;
        	if (speed > maxSpeed) maxSpeed = speed;
        	
        }
        
        System.out.println(maxSpeed);
		
	}
	
}
// You can have more than one class in a Java file as long 
// as only one is public

// implement comparable so an array of observations can be sorted
class Observation implements Comparable <Observation>{
	int time;
	int position;
	Observation(int t, int p) { time = t; position = p;}
	public int compareTo(Observation o) {
		if (time < o.time) return -1;
		else if (time == o.time) return 0;
		else return 1;
	}
	
}