How to write a “C” Program to evaluate the value of a function at non tabulated points by Lagrangian Interpolating Method.

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define MAX 10
void main()
{
int n,i,j;
float x[MAX],f[MAX],fp,lf,sum,xp;
printf("Input number of data points, n \n");
scanf("%d",&n);
printf("\n Input data points x(i) and values f(i) \n");
printf("(one set in each line) \n");
for(i=1;i<=n;i++)
scanf("%f  %f",&x[i],&f[i]);
printf("\n Input x at which interpolation is required. \n");
scanf("%f",&xp);
sum=0.0;
for(i=1;i<=n;i++)
{
lf=1.0;
for(j=1;j<=n;j++)
{
if(i!=j)
lf=lf*(xp-x[j])/(x[i]-x[j]);
}
sum=sum+lf*f[i];
}
fp=sum;
printf("LAGRANGIAN INTERPOLATION   \n\n\n");
printf("\n Interpolated function value  \n\n");
printf("\n at x=%f is %f  \n",xp,fp);
}