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 n, m, t;
int main() {
  scanf("%d%d", &n, &m);
  if (m == 3) {
    if (n == 3) puts("0 0\n100 0\n100 100");
    if (n == 4) puts("0 0\n100 0\n100 100\n50 1");
    if (n == 5) puts("-1");
    if (n == 6) puts("-1");
  } else {
    t = 0;
    for (int i = (0); i < (m); i++) {
      t += i;
      printf("%d %d\n", i, t);
    }
    t = 0;
    for (int i = (0); i < (n - m); i++) {
      t += i;
      printf("%d %d\n", 100000000 - i, t);
    }
  }
  return 0;
}