#include <bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
long long n, k;
long long ans = 0;
vector<vector<long long> > g;
pair<long long, vector<long long> > dfs(long long v, long long pr,
                                        long long h = 0) {
  vector<long long> d(k, 0);
  long long sz = 1;
  d[h % k] = 1;
  for (long long i = 0; i < g[v].size(); i++) {
    if (g[v][i] == pr) continue;
    pair<long long, vector<long long> > kek = dfs(g[v][i], v, h + 1);
    sz += kek.first;
    ans += kek.first * (n - kek.first);
    for (long long j = 0; j < k; j++) {
      for (long long y = 0; y < k; y++) {
        ans += ((k - ((y + j - ((2 * h) % k) + k) % k) + k) % k) * d[j] *
               kek.second[y];
      }
    }
    for (long long j = 0; j < k; j++) d[j] += kek.second[j];
  }
  return {sz, d};
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> k;
  g.resize(n);
  for (long long i = 1; i < n; i++) {
    long long a, b;
    cin >> a >> b;
    a--;
    b--;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  dfs(0, 0);
  cout << ans / k;
  return 0;
}
