#include <bits/stdc++.h>
template <class T>
void chkmin(T &x, T y) {
  if (x > y) x = y;
}
using ll = long long;

void mian() {
  int n, x;
  std::cin >> n >> x;
  std::vector<std::vector<std::pair<int, int>>> g(n + 1);
  std::vector<int> fi(n + 1), se(n + 1), dep(n + 1), fa(n + 1);
  for (int i = 0; i < n - 1; i++) {
    int u, v;
    std::cin >> u >> v;
    g[u].emplace_back(i * 2 + 2, v);
    g[v].emplace_back(i * 2 + 3, u);
  }
  for (int i = 1; i <= n; i++) {
    std::sort(g[i].begin(), g[i].end(), std::greater<>());
    fi[i] = g[i][0].second, se[i] = g[i].size() > 1 ? g[i][1].second : 0;
  }
  std::vector<std::vector<std::pair<int, int>>> ng((n - 1) * 2 + 2);
  std::vector<int> dis((n - 1) * 2 + 2, 1e9);
  for (int u = 1; u <= n; u++) {
    for (auto [k, v] : g[u]) {
      int w = fi[v] == u ? se[v] : fi[v];
      if (w) {
        int wk = w == fi[v] ? g[v][0].first : g[v][1].first;
        ng[wk].emplace_back(k, 1);
        if (fi[w] == v) {
          if (fi[v] == w) ng[wk ^ 1].emplace_back(k, 4);
          // else ng[k ^ 1].emplace_back(k, 3);
        }
      } else dis[k] = 0;
    }
  }
  std::queue<int> q;
  for (int i = 1; i <= (n - 1) * 2 + 1; i++)
    if (dis[i] == 0) q.push(i);
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    for (auto [v, w] : ng[u])
      if (dis[v] > dis[u] + w) dis[v] = dis[u] + w, q.push(v);
  }
  for (auto [k, v] : g[1]) {
    if (v == x) {
      std::cout << dis[k] << '\n';
      return;
    }
  }
  auto dfs = [&](auto &self, int u, int ff, int d) -> void {
    dep[u] = d, fa[u] = ff;
    for (auto [w, v] : g[u])
      if (v != ff) self(self, v, u, d + 1);
  };
  dfs(dfs, 1, 0, 0);
  int ans = 1e9;
  for (int i = 0; i <= n; i++) {
    for (auto [w, y] : g[x])
      if (dep[y] + (y != fa[x]) <= i) {
        chkmin(ans, i + dis[w ^ 1]);
      }
    x = fi[x];
  }
  std::cout << ans << '\n';
}
int main() { 
  std::cin.tie(0)->sync_with_stdio(0); 
  // freopen("toptree.in", "r", stdin);
  // freopen("toptree.out", "w", stdout);
  int t;
  std::cin >> t;
  while (t--) mian();
}