import java.util.Scanner;

public class Class_Point {

public static class Point {

private Double x;

private Double y;

public Point() {

this.x = 0.0;

this.y = 0.0;

}

public Point(Double x, Double y) {

this.x = x;

this.y = y;

}

public Point(Point p) {

this.x = p.x;

this.y = p.y;

}

public Double getX() {

return this.x;

}

public Double getY() {

return this.y;

}

public Double distance(Point secondP) {

return Math.sqrt((this.x - secondP.x) * (this.x - secondP.x) + (this.y - secondP.y) * (this.y - secondP.y));

}

public static Double distance(Point a, Point b) {

return Math.sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));

}

}

public static void main(String args[]) {

Scanner in = new Scanner(System.in);

int t = in.nextInt();

while(t-- > 0) {

double a = in.nextDouble();

double b = in.nextDouble();

double c = in.nextDouble();

double d = in.nextDouble();

Point x = new Point(a, b);

Point y = new Point(c, d);

System.out.printf("%.4f\n", Point.distance(x, y));

}

}

}