#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3c3c3c3c;
const long long LINF = 0x3c3c3c3c3c3c3c3cL;
const int maxN = 1 << 18;
const int maxK = 5;
vector<int> g[maxN];
int k;
struct DP {
  long long sum[maxK];
  long long cnt[maxK];
  DP() {
    memset(sum, 0, sizeof(sum));
    memset(cnt, 0, sizeof(cnt));
  }
  DP up() {
    DP res;
    for (int o = 0; o < k; o++) {
      int o2 = (o + 1) % k;
      res.cnt[o2] += cnt[o];
      res.sum[o2] += sum[o];
      if (o + 1 >= k) {
        res.sum[o2] += cnt[o];
      }
    }
    return res;
  }
  DP& operator+=(DP& other) {
    for (int o = 0; o < k; o++) {
      cnt[o] += other.cnt[o];
      sum[o] += other.sum[o];
    }
    return *this;
  }
  DP& operator-=(DP& other) {
    for (int o = 0; o < k; o++) {
      cnt[o] -= other.cnt[o];
      sum[o] -= other.sum[o];
    }
    return *this;
  }
};
DP dp[maxN];
long long ans = 0;
void dfs(int v, int p) {
  for (auto u : g[v]) {
    if (u == p) {
      continue;
    }
    dfs(u, v);
    DP cur = dp[u].up();
    dp[v] += cur;
  }
  for (auto u : g[v]) {
    if (u == p) {
      continue;
    }
    DP dp_v = dp[v];
    DP cur = dp[u].up();
    dp_v -= cur;
    for (int o_cur = 0; o_cur < k; o_cur++) {
      for (int o_v = 0; o_v < k; o_v++) {
        ans += dp_v.sum[o_v] * cur.cnt[o_cur] + cur.sum[o_cur] * dp_v.cnt[o_v];
        ans +=
            max(0, (o_v + o_cur + k - 1) / k) * cur.cnt[o_cur] * dp_v.cnt[o_v];
      }
    }
  }
  for (int o = 0; o < k; o++) {
    ans += 2 * (dp[v].sum[o] + dp[v].cnt[o] * (int(o > 0)));
  }
  dp[v].cnt[0]++;
}
int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n >> k;
  for (int i = 0; i < n - 1; i++) {
    int v, u;
    cin >> v >> u;
    g[v].push_back(u);
    g[u].push_back(v);
  }
  dfs(1, 0);
  cout << ans / 2 << endl;
  return 0;
}
