#include<stdio.h>
#include<math.h>

int main(){
    int n;
    if(scan("%d",&n)!=1)
    {
        printf("invalid input\n");
        return 0;
    
    }
    if(n<=0){
        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\n");
            return 0;
        }
        double distance = sqrt(pow(x2 - x1,2)+ pow(y2 - y1,2));
        printf("%.2f\n",distance);
    }
    return 0;
}