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

const float pi = 4.0 * atan(1.0);

main(){
   float P, E, r, f;
   P = 1.5 * pow(10.0 , -9.0);
   E = 8.85 * pow(10,-12);
   r = 1.0;
   f = P / ( 2 * pi * E * r);
   printf("Electric field is = %f",f);
   while(!kbhit()){
   }
}