#include<stdio.h>
int main()
{
int R;
float c;
 printf("enter the radius of the circle--");
 scanf("%d",&R);
 printf("\n");
 if(R>=1||R<=100)
  {
   c=2*3.14159*R;
   printf("%d",c);
   }
   else
   {
   printf("enter the valid radius");
   }
return 0;   
}   
  
