#include <bits/stdc++.h>
using namespace std;
const int maxn = 3000 + 10;
int sum, d[maxn], dp[maxn][2];
vector<pair<int, int> > edge[maxn];
int min(int a, int b) { return a < b ? a : b; }
void dfs(int u, int f, int w) {
  if (f == -1) {
    sum = 0;
    d[u] = 0;
    dp[u][0] = dp[u][1] = 0;
  } else {
    dp[u][1] = dp[f][1] + w;
    dp[u][0] = min(dp[f][0], dp[f][1]) + !w;
    d[u] = d[f] + w;
  }
  for (vector<pair<int, int> >::iterator it = edge[u].begin();
       it != edge[u].end(); it++) {
    int to = it->first;
    int wt = it->second;
    if (to == f) continue;
    sum += wt;
    dfs(to, u, wt);
  }
}
int main() {
  int n, u, v, ret = maxn;
  cin >> n;
  for (int i = 0; i < n - 1; i++) {
    cin >> u >> v;
    edge[u].push_back(make_pair(v, 0));
    edge[v].push_back(make_pair(u, 1));
  }
  for (int i = 1; i <= n; i++) {
    dfs(i, -1, 0);
    for (int j = 1; j <= n; j++) {
      ret = min(ret, sum + min(dp[j][0], dp[j][1]) - d[j]);
    }
  }
  cout << ret << endl;
  return 0;
}
