import java.util.Arrays;
import java.util.Scanner;

/*
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/**
 *
 * @author cteam056
 */
public class Cable {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        int n = s.nextInt();
        double [][] c = new double[n][3];
        for(int i=0;i<n;i++){
            c[i][0]=s.nextInt();
            c[i][1]=s.nextInt();
            c[i][2]=Math.abs((c[i][0]+c[i][1])*Math.sqrt(2)/2);
        }
        double max = 0;
        double x=0;
        double y=0;
        for (int j=0;j<n;j++){
            if(c[j][2]>max){
                x=c[j][0];
                y=c[j][1];
                max = c[j][2];
            }
        }
        double pX1;
        double pY1;
        double ca = y-x;
        
        double range  = 2*max;
        System.out.println(range);
    }
}