//
//long long gcd(long long a, long long b) {
//  if (a == 0) {
//      return b;
//  }
//  return gcd(b % a, a);
//}
//
//long long lcm(long long a, long long b) {
//  return a * b / gcd(a, b);
//}

vector <vector <int>> v;
vector <int> maxh;
vector <bool> used;

void dfs1(int node, vector <int> &dist, int length) {
    dist[node] = length;
    used[node] = 1;
    for (int i = 0; i < v[node].size(); i++)
    {
        if (!used[i]) {
            dfs1(v[node][i], dist, length + 1);
        }
    }
}

void dfs2(int node, int length)
{
    used[node] = 1;
    maxh[node] = length;
    for (int i = 0; i < v[node].size(); i++) {
        if (!used[i]) {
            dfs2(i, length + 1);
            maxh[node] = max(maxh[node], maxh[i]);
        }
    }
}

void task1() {
    int n, x;
    cin >> n >> x;
    --x;
    v.resize(n);
    used.resize(n + 1);
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        --a, --b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    vector <vector <int>> d(2, vector <int> (n));
    used.assign(n, false);
    dfs1(0, d[0], 0);
    used.assign(n, false);
    dfs1(x, d[1], 0);
    used.assign(n, false);
    maxh.resize(n);
    dfs2(0, 0);
    int res = 0;
    for (int i = 0; i < n; i++) {
        if (d[1][i] < d[0][i]) {
            res = max(res, maxh[i]);
        }
    }
    cout << 2 * res;
}

int main() {
    task1();
    system("PAUSE");
}