#include <stdio.h>

int main() {
  int n, i, j = 1;
  double xp, yp, f1, f2 = 0;

  printf("Enter the number of inputs: ");
  scanf("%d", &n);

  double x[n], y[n];

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

  yp = y[0];

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

  do {
    for (i = 0; i < n - 1; i++) 
      y[i] = ((y[i + 1] - y[i]) / (x[i + j] - x[i]));

    f1 = 1;

    for (i = 0; i < j; i++) {
      f1 *= (xp - x[i]);
    }

    f2 += (y[0] * f1);
    j++;
  } while ((--n) > 1);

  yp += f2;
  
  printf("Interpolated value for %lf is %lf.", xp, yp);
}