Please help me.. What's wrong in this code?


#include <stdio.h>
#include <math.h>

#define MAX_COUNT 100
#define PI 2. * acos (0.)


struct vertices
{
  double x;
  double y;
};

double solve (struct vertices *vert, int n, double r);

int main ()
{
  struct vertices vert[MAX_COUNT];
  double r;
  double res;
  int n;
  int i;

  if (scanf ("%d", &n) != 1)
    return -1;
  if (n < 1 || n > MAX_COUNT)
    return -2;

  if (scanf ("%lg", &r) != 1)
    return -3;
  if (r < 0.)
    return -4;

  for (i = 0; i < n; i++){
    if (scanf ("%lg %lg", &vert[i].x, &vert[i].y) != 2)
      return -5;
    if (fabs (vert[i].x) > 101. || fabs (vert[i].y) > 101.)
      return -6;
  }

  res = solve (vert, n, r);

  res = (double)((int)(res * 100));
  res /= 100;

  printf ("%.2lf\n", res);

  return 0;
}

double solve (struct vertices *vert, int n, double r)
{
  double res = 0.;
  double abs_x, abs_y;
  int i, t;

  for (i = 0; i < n; i++){
    t = (i + 1) % n;
    abs_x = (vert[i].x - vert[t].x) * (vert[i].x - vert[t].x);
    abs_y = (vert[i].y - vert[t].y) * (vert[i].y - vert[t].y);
    res += sqrt (abs_x + abs_y);
  }

  res += r * PI * 2.;

  return res;
}