import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Scanner;
class Main
{
{
double x1, y1, z1, x, y, S;
Scanner in
= new Scanner
(System.
in); x = in.nextInt();
y = in.nextInt();
x1 = in.nextInt();
y1 = in.nextInt();
z1 = in.nextInt();
S
= Math.
sqrt((x1
- x
)*(x1
- x
) + (y1
-y
)*(y1
-y
) + z1
*z1
); System.
out.
printf("%.3f",
1/S
); }
}
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