#include <bits/stdc++.h>
using namespace std;
const int MAXN = (int)(1e6 + 7);
const long long oo = (long long)(1e18);
const double esp = (double)1e-6;
const long long MOD = (long long)(1e9 + 7);
int n, x, y, fre[MAXN];
vector<int> adj[MAXN];
void dfs(int u, int t) {
  if (u == t) return;
  fre[u] = 0;
  for (int i = 0; i < (int)adj[u].size(); i++) {
    int v = adj[u][i];
    if (fre[v]) {
      dfs(v, t);
    }
  }
}
int main() {
  while (cin >> n >> x >> y) {
    for (int i = 1; i <= n; i++) adj[i].clear();
    int a, b;
    for (int i = 0; i < n - 1; i++) {
      cin >> a >> b;
      adj[a].push_back(b);
      adj[b].push_back(a);
    }
    long long res = 1LL * n * (n - 1) / 2;
    for (int i = 1; i <= n; i++) fre[i] = 1;
    dfs(x, y);
    long long cnt2 = 0, cnt1 = 0;
    for (int i = 1; i <= n; i++) {
      if (fre[i]) {
        ++cnt1;
      }
      fre[i] = 1;
    }
    dfs(y, x);
    for (int i = 1; i <= n; i++) {
      if (fre[i]) {
        ++cnt2;
      }
      fre[i] = 1;
    }
    long long z = cnt2 * cnt1;
    cout << res + res - z << endl;
  }
  return 0;
}
