package chelper;

import java.util.Arrays;

import io.InputReader;
import io.OutputWriter;
import misc.SimpleSavingChelperSolution;


public class MAXPRODU extends SimpleSavingChelperSolution {

  public static final long MOD = 1000000007;

  public void solve(int testNumber, InputReader in, OutputWriter out) {
    wrapSolve(testNumber, in, out);
  }

  @Override
  public void solve(int testNumber) {
    long n = in.nextLong();
    long k = in.nextLong();

    if (n < (1 + k) * k / 2) {
      out.println(-1);
      return;
    }

    long[] a = new long[(int) k];

    long next = 1;
    long left = n;
    int i = 0;

    while (i < k) {
      long sum = (next + next + k - i - 1) * (k - i) / 2;
      if (sum > left) {
        left -= a[i];
        i++;
        continue;
      }

      a[i] = next;
      next++;
    }

    long res = 1;
    for (long j : a) {
      res *= (j * j - j) % MOD;
      res %= MOD;
    }

    out.println(res);
  }
}