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() {
  int i, j, k;
  int n, m;
  scanf("%d%d", &n, &m);
  if (m == 3) {
    switch (n) {
      case 3:
        printf("0 0\n");
        printf("3 0\n");
        printf("0 3\n");
        break;
      case 4:
        printf("0 0\n");
        printf("3 0\n");
        printf("0 3\n");
        printf("1 1\n");
        break;
      case 5:
      case 6:
        printf("-1\n");
        break;
    }
  } else {
    k = 10000000;
    for (i = 0; i < m; i++) printf("%d %d\n", i, k + i * i);
    for (i = 0; i < n - m; i++) printf("%d %d\n", i, -k - i * i);
  }
  return 0;
}