Problem: Convexity of a set of points on the plane is the size of the largest subset of points that form a convex polygon. Your task is to build a set of n points with the convexity of exactly m. Your set of points should not contain three points that lie on a straight line.

Input

The single line contains two integers n and m (3 ≤ m ≤ 100, m ≤ n ≤ 2m).

Output

If there is no solution, print "-1". Otherwise, print n pairs of integers — the coordinates of points of any set with the convexity of m. The coordinates shouldn't exceed 108 in their absolute value.

Examples

Input

4 3


Output

0 0
3 0
0 3
1 1


Input

6 3


Output

-1


Input

6 6


Output

10 0
-10 0
10 1
9 1
9 -1
0 -2


Input

7 4


Output

176166 6377
709276 539564
654734 174109
910147 434207
790497 366519
606663 21061
859328 886001

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  int N, M;
  cin >> N >> M;
  if (M == 3) {
    if (N == 3) {
      cout << 0 << ' ' << 0 << endl;
      cout << 0 << ' ' << 1 << endl;
      cout << 1 << ' ' << 0 << endl;
      return 0;
    }
    if (N == 4) {
      cout << 0 << ' ' << 0 << endl;
      cout << 0 << ' ' << 10 << endl;
      cout << 10 << ' ' << 0 << endl;
      cout << 1 << ' ' << 1 << endl;
      return 0;
    }
    if (N >= 5) {
      cout << -1 << endl;
      return 0;
    }
  }
  int first = 10000000;
  for (int i = (0); i <= (M - 1); i++)
    cout << i << ' ' << first + i * i << endl;
  for (int i = (0); i <= (N - M - 1); i++)
    cout << i << ' ' << -first - i * i << endl;
  return 0;
}