Area of circle circumstances in C program

Area of circle circumstances in C program 

#include<stdio.h>
#include<math.h>
main()
{
    float pi,m,n,o,r;
    scanf("%f",&r);
    pi=3.1416;
    m=pi*r*r;
    n=2*pi*r;
    o=2*r;
    printf("the area=%f\nthe parandrom=%f\nthe bass=%f\n",m,n,o);
    return 0;
}