#include <stdio.h>
#include <math.h>
int main()
{
    int n;
    if (scanf("%d" , &n) != 1)
    {
        printf("Invalid input");
        return 0;
    }
    for(int i = 0; i < n; i++)
    {
        double x1, y1, x2, y2;
        if (scanf("%1f %1f %1f %1f", &x1, &y1, &x2, &y2) !=4)
        {
            printf("Invalid input");
            return 0;
        }
        double distance = sqrt(pow(x2 - x1, 2) + pow(y2 - y1 , 2));
        printf("%.21f\n" , distance);
    }
    return 0;
}