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

int main()
{
  float r1 = 0,r2 = 0 , r3=0;
  printf("Enter the values of the 3 registers in format: r1,r2,r3 ");
  scanf("%f,%f,%f",&r1,&r2,&r3);
  
  float rEq = (r1*r2*r3)/(r1*r2 + r2*r3 +r3*r1);
  
  printf("The combined resistance, in ohms is %f\n",rEq);
  
  return 0;
}