SIMPSON'S 1/3 RULE IN C

//PROGRAM TO USE SIMPSON'S 1/3 RULE TO FIND F(X)=e^x^2
#include<stdio.h>
#include<math.h>
float fun(float);
int main()
{
  int i,n;
  float x[10],y[10],h,sum,s1,s2,l,u;//l = lower limit,u=upperlimit

  printf("Enter number of intervals :\n");
  scanf("%d",&n);
  if(i%2==0)
  {
     printf("Enter the lower limit and upper limit :\n");
     scanf("%f%f",&l,&u);
      h=(u-l)/n;

     for(i=0;i<=n;i++)
      {
           x[i]=(i*h)+l;
          printf("x[%d]=%f\t",i,x[i]);
            y[i]=fun(x[i]);
          printf("y[%d]=%f\t",i,y[i]);
       }
    sum=y[0]+y[n];
   for(i=1;i<n;i++)
   {
      if(i%2==0)
        s1+=y[i];
       else
        s2+=y[i];
     }
   sum=h/3*(sum+4*s2+2*s1);

   printf("Integral value is : %f\n",sum);
   }
   else
  printf("This rule is not applicable .\n");
 return 0;
}
float fun(float)
{
   float f;
   f=exp(x*x);
   return 0;
}