C Program to calculate area of circle using radius (or) diameter

//Program to calculate area of circle using radius (or) diameter.
#include<stdio.h>
int main()
{
    float n,r,d,area;
    printf("\n You want to calculate area of circle using");
    printf("\n 1.Radius \n 2.Diameter");
    printf("\n Enter your choice:");
    scanf("%g",&n);
    if(n==1)
          {
        printf("\n Enter radius:");
        scanf("%g",&r);       
        printf("\n Area of circle = %g \n",3.14*2*r);
          }
       
    else if(n==2)
          {
        printf("\n Enter diameter:");
        scanf("%g",&d);       
        printf("\n Area of circle = %g \n",3.14*d);
          }
    else
        printf("\n Invalid choice \n");
return 0;
}