#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("%lf %lf %lf %lf", &x1, &y1, &x2, &y2) != 4) {
            printf("Invalid input");
            return 0;
        }
        double distance = sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
        printf("%.21f", distance);
        
        if (i < n - 1) { 
            printf("\n");
        }
        return 0;
}