* package whatever; // don't place package name! */
import java.util.*;
import java.lang.*;
import java.io.*;
/* Name of the class has to be "Main" only if the class is public. */
public class Main
{
{
// your code goes here
String s
[] =inp.
readLine().
split(" "); long r
=Long.
parseLong(s
[0]); long x
=Long.
parseLong(s
[1]); long y
=Long.
parseLong(s
[2]); long x1
=Long.
parseLong(s
[3]); long y1
=Long.
parseLong(s
[4]); // System.out.println((x-x1)*(x-x1));
// System.out.println((y-y1)*(y-y1));
long num=(x-x1)*(x-x1) + (y-y1)*(y-y1);
// System.out.println(num);
double ans
=Math.
sqrt(num
); double sol=(ans)/(2*r);
}
}
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