#include <bits/stdc++.h>
using namespace std;
class CPoint{
public:
int x,y;
CPoint(int x,int y){
this->x=x;
this->y=y;
}
};
double operator-(CPoint&a,CPoint&b){
return sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));
}
int main() {
int n;
cin>>n;
for(int i=0;i<n;++i){
int a,b,c,d;
cin>>a>>b>>c>>d;
CPoint A(a,b),B(c,d);
printf("%.2f\n",A-B);
}
}
// 64 位输出请用 printf("%lld")

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