#include <stdio.h>

int main() {
  double xp, yp = 0, p;
  int i, j, n;

  printf("Number of inputs: ");
  scanf("%d", &n);

  double x[n], y[n];
  printf("Input sample space:\n");

  for (i = 0; i < n; i++) {
    printf("x%d: ", i);
    scanf("%lf", x + i);
    printf("y%d: ", i);
    scanf("%lf", y + i);
  }

  printf("Enter interpolation point x: ");
  scanf("%lf", &xp);

  for (i = 0; i < n; i++) {
    p = 1;
    for (j = 0; j < n; j++) {
      if (i != j) {
        p *= (xp - x[j]) / (x[i] - x[j]);
      }
    }
    yp += p * y[i];
  }
  printf("Interpolated value for %lf is %lf.", xp, yp);
}