The minimum radius calculation of bicycle pedal rod

pow () pow (double x, double y) Returns the y-th power of x.

#include <iostream>
#include<cmath>
#define pi 3.1415926
using namespace std;
int main()
{
 float d,p,s,r3,r;
 cin>>d>>p>>s;
 r3=(d*p)/(pi*s);
 r=pow(r3,1.0/3.0);
 printf("%.6f",r);
}