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>
int main(void) {
  int i, j, k, n, m;
  while (scanf("%d%d", &n, &m) != EOF) {
    if (3 == m) {
      if (3 == n)
        printf("0 0\n0 1\n1 0\n");
      else if (4 == n)
        printf("0 0\n3 0\n0 3\n1 1\n");
      else
        printf("-1\n");
      continue;
    } else {
      j = 1;
      k = 1;
      printf("%d %d\n", -1, 0);
      for (i = 2; i <= m; i++) printf("%d %d\n", j++, k), k += i;
      j = 1000000;
      for (i = 1; i <= n - m; i++) printf("%d %d\n", j, k--), j += i;
    }
  }
  return 0;
}