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;
const int MAXN = 10 + 1000;
const int INF = int(1e7);
int n, m;
int main() {
  ({
    int neg = 0;
    n = 0;
    char ch;
    for (ch = getchar(); ch < '0' || ch > '9'; ch = getchar())
      if (ch == '-') neg = 1 - neg;
    n = ch - 48;
    for (ch = getchar(); ch >= '0' && ch <= '9'; ch = getchar())
      n = (n << 3) + (n << 1) + ch - 48;
    if (neg) n = -n;
  });
  ({
    int neg = 0;
    m = 0;
    char ch;
    for (ch = getchar(); ch < '0' || ch > '9'; ch = getchar())
      if (ch == '-') neg = 1 - neg;
    m = ch - 48;
    for (ch = getchar(); ch >= '0' && ch <= '9'; ch = getchar())
      m = (m << 3) + (m << 1) + ch - 48;
    if (neg) m = -m;
  });
  if (m == 3 && (n == 5 || n == 6))
    printf("-1\n");
  else {
    for (int i = (0), _b = (m); i < _b; ++i) printf("%d %d\n", i, i * i + INF);
    for (int i = (0), _b = (n - m); i < _b; ++i)
      printf("%d %d\n", i, -i * i - INF);
  }
  return 0;
}