#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\n", distance);
    }
    
    return 0;
    
}