#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll dp_sum[5][200001];
ll dp_no[5][200001];
bool vis[200001];
vector<int> adj[200001];
int k;
ll ans = 0LL;
ll ans2 = 0LL;
void dfs(int v, int par) {
  vis[v] = 1;
  for (auto u : adj[v]) {
    if (u != par) {
      dfs(u, v);
      for (int i = 1; i <= k; i++) {
        dp_sum[i % k][v] += dp_no[i - 1][u] + dp_sum[i - 1][u];
        dp_no[i % k][v] += dp_no[i - 1][u];
      }
    }
  }
  for (auto u : adj[v]) {
    if (u == par) continue;
    for (int i = 0; i < k; i++) {
      for (int j = 0; j < k; j++) {
        ll no_paths = dp_no[(i + k - 1) % k][u] *
                      (dp_no[j][v] - dp_no[(j + k - 1) % k][u]);
        ans += (dp_sum[(i + k - 1) % k][u] + dp_no[(i + k - 1) % k][u]) *
               (dp_no[j][v] - dp_no[(j + k - 1) % k][u]);
        ans += (dp_sum[j][v] - dp_sum[(j + k - 1) % k][u] -
                dp_no[(j + k - 1) % k][u]) *
               dp_no[(i + k - 1) % k][u];
        ans += ((k + k - i - j) % k) * no_paths;
      }
    }
  }
  for (int i = 0; i < k; i++) {
    ans2 += dp_sum[i][v] + ((k - i) % k) * dp_no[i][v];
  }
  dp_no[0][v]++;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n >> k;
  for (int i = 0; i < n - 1; i++) {
    int a, b;
    cin >> a >> b;
    adj[a].push_back(b);
    adj[b].push_back(a);
  }
  dfs(1, -1);
  cout << ll(ans / ll(k + k)) + ll(ans2 / ll(k)) << endl;
}
