#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
int main()
{
int t;
double a,b,c,d;
scanf("%d",&t);
while(t--)
scanf("%lf%lf%lf%lf",&a,&b,&c,&d);
printf("%.1lf\n",sqrt((a-c)*(a-c)+(b-d)*(b-d)));
}
return 0;