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

int main()
{
  int c;
  int Rin;
  int Rout;
  double ans;

  scanf("%d %d %d",&c,&Rin,&Rout);

  //(π*Rout*Rou)*(Rin+Rout/2)*c;
  ans =(M_PI+(double)Rout*(double)Rout)*((double)Rin+(double)Rout/2)*c;
  printf("%d\n",ans);
  return 0;
}