#include <bits/stdc++.h>
using namespace std;
clock_t t1 = clock();
long long _mergeSort(long long arr[], long long temp[], long long left,
                     long long right);
long long merge(long long arr[], long long temp[], long long left,
                long long mid, long long right);
long long mergeSort(long long arr[], long long array_size) {
  long long *temp = (long long *)malloc(sizeof(long long) * array_size);
  return _mergeSort(arr, temp, 0, array_size - 1);
}
long long _mergeSort(long long arr[], long long temp[], long long left,
                     long long right) {
  long long mid, inv_count = 0;
  if (right > left) {
    mid = (right + left) / 2;
    inv_count = _mergeSort(arr, temp, left, mid);
    inv_count += _mergeSort(arr, temp, mid + 1, right);
    inv_count += merge(arr, temp, left, mid + 1, right);
  }
  return inv_count;
}
long long merge(long long arr[], long long temp[], long long left,
                long long mid, long long right) {
  long long i, j, k;
  long long inv_count = 0;
  i = left;
  j = mid;
  k = left;
  while ((i <= mid - 1) && (j <= right)) {
    if (arr[i] <= arr[j]) {
      temp[k++] = arr[i++];
    } else {
      temp[k++] = arr[j++];
      inv_count = inv_count + (mid - i);
    }
  }
  while (i <= mid - 1) temp[k++] = arr[i++];
  while (j <= right) temp[k++] = arr[j++];
  for (i = left; i <= right; i++) arr[i] = temp[i];
  return inv_count;
}
int main() {
  ios::sync_with_stdio(false);
  long long n, k;
  cin >> n >> k;
  long long ans = 0;
  if (n == 1 || k == 0) {
    cout << 0 << "\n";
    return 0;
  } else {
    if (k > n / 2) k = n / 2;
    long long a[n];
    for (__typeof(0) i = (0); i != (n - 1) + 1 - 2 * ((0) > (n - 1));
         i += 1 - 2 * ((0) > (n - 1))) {
      a[i] = i + 1;
    }
    long long j = 0;
    while (k--) {
      long long temp = a[n - j - 1];
      a[n - j - 1] = a[j];
      a[j] = temp;
      j++;
    }
    ans = mergeSort(a, n);
  }
  cout << ans << "\n";
  return 0;
}
