#include <iostream>
#include<cmath>
#include<iomanip>
using namespace std;
int main(){
    if(!(cin>>n)){
        cout<<"invalid input";
        return 0;
    }
    for (int i = 0; i<n;i++){
        double x1,y1,x2,y2;
        if(!(cin>>x1>>y1>>x2>>y2)){
            cout<<"invalid input";
            return 0;
        }
        double dist = sqrt(pow(x2-x1,2)+pow(y2-y1,2));
        cout<<fixed<<setprecision(2)<<dist<<endl;
    }
    return 0;
}