#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const double EPS = 1e-9;
void Debug(int i) { printf("\n----Debug %d-----\n", i); }
const double PI = acos(-1.0);
int sgn(double x) {
  if (fabs(x) < EPS) return 0;
  if (x < 0) return -1;
  return 1;
}
struct point {
  double x, y;
  point(){};
  int id;
  point(double x0, double y0) { x = x0, y = y0; }
  point operator-(const point &b) const { return point(x - b.x, y - b.y); }
  point operator+(const point &b) const { return point(x + b.x, y + b.y); }
  double operator*(const point &b) const { return x * b.x + y * b.y; }
  double operator^(const point &b) const { return x * b.y - y * b.x; }
  void transXY(double B) {
    double tx = x, ty = y;
    x = tx * cos(B) - ty * sin(B);
    y = tx * sin(B) + ty * cos(B);
  }
  bool operator==(const point &b) const {
    return (sgn(x - b.x) == 0 && sgn(y - b.y) == 0);
  }
  double len() {
    double t = x * x + y * y;
    return sqrt(t);
  }
  point unit() {
    double l = len();
    double xx = x / l;
    double yy = y / l;
    return point(xx, yy);
  }
  point neg() { return point(-x, -y); }
};
struct line {
  point s, e;
  line(){};
  line(point a, point b) { s = a, e = b; }
  pair<int, point> operator&(const line &b) const {
    point res = s;
    if (sgn((s - e) ^ (b.s - b.e)) == 0) {
      if (sgn((s - b.e) ^ (b.s - b.e)) == 0)
        return make_pair(0, res);
      else
        return make_pair(1, res);
    }
    double t = ((s - b.s) ^ (b.s - b.e)) / ((s - e) ^ (b.s - b.e));
    res.x += (e.x - s.x) * t;
    res.y += (e.y - s.y) * t;
    return make_pair(2, res);
  }
  point v;
  point get_point(double t) { return point(s.x + v.x * t, s.y + v.y * t); }
};
struct circle {
  point heart;
  double r;
};
double dist(point a, point b) {
  double xx = (a.x - b.x), yy = (a.y - b.y);
  return sqrt(xx * xx + yy * yy);
}
int main() {
  int a, x, y;
  cin >> a >> x >> y;
  int xx = x;
  x = fabs(x);
  int d = y / a;
  if (y % a == 0) {
    puts("-1");
    return 0;
  } else {
    if (d == 1 || d == 0 || (d & 1)) {
      int ans = -1;
      if (d == 1 || d == 0)
        ans = d + 1;
      else
        ans = 1 + (d + 1) / 2 * 3 - 2;
      if ((double)x < a / 2.0) {
        printf("%d\n", ans);
      } else {
        printf("-1\n");
      }
    } else {
      if (x == 0) {
        puts("-1");
        return 0;
      }
      if (x < a) {
        int ans = 1 + d / 2 * 3 - (xx < 0);
        printf("%d\n", ans);
      } else {
        printf("-1\n");
      }
    }
  }
  return 0;
}

### Prompt

Develop a solution in cpp to the problem described below:

So nearly half of the winter is over and Maria is dreaming about summer. She's fed up with skates and sleds, she was dreaming about Hopscotch all night long. It's a very popular children's game. The game field, the court, looks as is shown in the figure (all blocks are square and are numbered from bottom to top, blocks in the same row are numbered from left to right). Let us describe the hopscotch with numbers that denote the number of squares in the row, staring from the lowest one: 1-1-2-1-2-1-2-(1-2)..., where then the period is repeated (1-2).

<image>

The coordinate system is defined as shown in the figure. Side of all the squares are equal and have length a.

Maria is a very smart and clever girl, and she is concerned with quite serious issues: if she throws a stone into a point with coordinates (x, y), then will she hit some square? If the answer is positive, you are also required to determine the number of the square.

It is believed that the stone has fallen into the square if it is located strictly inside it. In other words a stone that has fallen on the square border is not considered a to hit a square.

Input

The only input line contains three integers: a, x, y, where a (1 ≤ a ≤ 100) is the side of the square, x and y ( - 106 ≤ x ≤ 106, 0 ≤ y ≤ 106) are coordinates of the stone.

Output

Print the number of the square, inside which the stone fell. If the stone is on a border of some stone or outside the court, print "-1" without the quotes.

Examples

Input

1 0 0


Output

-1


Input

3 1 1


Output

1


Input

3 0 10


Output

5


Input

3 0 7


Output

-1


Input

3 4 0


Output

-1

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const double EPS = 1e-9;
void Debug(int i) { printf("\n----Debug %d-----\n", i); }
const double PI = acos(-1.0);
int sgn(double x) {
  if (fabs(x) < EPS) return 0;
  if (x < 0) return -1;
  return 1;
}
struct point {
  double x, y;
  point(){};
  int id;
  point(double x0, double y0) { x = x0, y = y0; }
  point operator-(const point &b) const { return point(x - b.x, y - b.y); }
  point operator+(const point &b) const { return point(x + b.x, y + b.y); }
  double operator*(const point &b) const { return x * b.x + y * b.y; }
  double operator^(const point &b) const { return x * b.y - y * b.x; }
  void transXY(double B) {
    double tx = x, ty = y;
    x = tx * cos(B) - ty * sin(B);
    y = tx * sin(B) + ty * cos(B);
  }
  bool operator==(const point &b) const {
    return (sgn(x - b.x) == 0 && sgn(y - b.y) == 0);
  }
  double len() {
    double t = x * x + y * y;
    return sqrt(t);
  }
  point unit() {
    double l = len();
    double xx = x / l;
    double yy = y / l;
    return point(xx, yy);
  }
  point neg() { return point(-x, -y); }
};
struct line {
  point s, e;
  line(){};
  line(point a, point b) { s = a, e = b; }
  pair<int, point> operator&(const line &b) const {
    point res = s;
    if (sgn((s - e) ^ (b.s - b.e)) == 0) {
      if (sgn((s - b.e) ^ (b.s - b.e)) == 0)
        return make_pair(0, res);
      else
        return make_pair(1, res);
    }
    double t = ((s - b.s) ^ (b.s - b.e)) / ((s - e) ^ (b.s - b.e));
    res.x += (e.x - s.x) * t;
    res.y += (e.y - s.y) * t;
    return make_pair(2, res);
  }
  point v;
  point get_point(double t) { return point(s.x + v.x * t, s.y + v.y * t); }
};
struct circle {
  point heart;
  double r;
};
double dist(point a, point b) {
  double xx = (a.x - b.x), yy = (a.y - b.y);
  return sqrt(xx * xx + yy * yy);
}
int main() {
  int a, x, y;
  cin >> a >> x >> y;
  int xx = x;
  x = fabs(x);
  int d = y / a;
  if (y % a == 0) {
    puts("-1");
    return 0;
  } else {
    if (d == 1 || d == 0 || (d & 1)) {
      int ans = -1;
      if (d == 1 || d == 0)
        ans = d + 1;
      else
        ans = 1 + (d + 1) / 2 * 3 - 2;
      if ((double)x < a / 2.0) {
        printf("%d\n", ans);
      } else {
        printf("-1\n");
      }
    } else {
      if (x == 0) {
        puts("-1");
        return 0;
      }
      if (x < a) {
        int ans = 1 + d / 2 * 3 - (xx < 0);
        printf("%d\n", ans);
      } else {
        printf("-1\n");
      }
    }
  }
  return 0;
}

```