// editor3
#include <stdio.h>


  int main() {
      int n, i;
      float x1,y1,x2,y2;
      float distance;
      
      
      //read number of test cases
      if(scanf("%d", &n)!=1) {
          printf("Invalid input");
          return 0;
      } 
      
      for(int i=0; i<n; i++) {
          if (scanf("%f %f %f %f ,&x1,&y1,&x2,&y2")!=4) {
              printf("Invalid input");
              return 0;
          }
          
          dx=x2-x1;
          dy=y2-y1;
          
          /*Manual square root using Newton-Raphson*/
          distance=dx*dx+dy*dy;
          float guess = distance/2.0;
          int j;
          for (j=0;j<10; j++){
              guess=(guess+distance/guess)/2.0;
              
          }
          printf("%.2f,guess");
          
          if(i<n-1)
          printf("/n");
          }
          return 0;
  }