Simpson’s 1/3rd program in c for non tabulates values

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define f(x) (x*x*x*x)

void main()
{
  int i,n;
  float h,s,s2,s4,integral,a,b;
  clrscr();
  printf("enter a and b then n :");
  scanf("%f%f%d",&a,&b,&n);
  h=(b-a)/(n);
  s=f(a)+f(b);
  s2=0;
  s4=0;
  for(i=1;i<=(n-2);i=i+2)
  {
    s2 = s2+f(a+i*h);
    s4 = s4+f(a+(i+1)*h);
  }
  integral=(h/3)*(s+2*s2+4*s4);
  printf("integral is %f",integral);
  getch();
}