Find the value of sphere a program make c++

My code here is Find the Value of sphere.

                 Here the code

  #include<stdio.h>

int main()
{
int tw = 4, pi1= 22, pi2= 7, r;

printf("Enter the 'r' : ");
scanf("%d",&r);
float res = tw*pi1*r*r;
float result = res/pi2;
printf("The Area of sphere is : %f",result);

}