// Dùng cho N nhỏ, tham khảo ý tưởng
// O(N^2) hoặc O(N^3)
// Code đầy đủ quá dài, chỉ minh họa logic
int solve_small() {
    // Tính L(x) cho mọi x
    // Duyệt tất cả cặp (u, v) không kề nhau
    // Tính min(L(u), L(v))
    // Lấy max
    return 0;
}

int n, c1, c2;
vector<pair<int, int>> adj[100005];
bool on_path[100005];
long long L[100005];
int parent[100005];
int path_idx[100005];
int label[100005];

void dfs_path(int u, int p) {
    parent[u] = p;
    for (auto& edge : adj[u]) {
        int v = edge.first;
        if (v != p) dfs_path(v, u);
    }
}

void dfs_L(int u, int p, long long current_flow) {
    long long sum = 0;
    for (auto& edge : adj[u]) {
        int v = edge.first;
        int w = edge.second;
        if (v == p) continue;
        if (on_path[v]) continue; // Cắt nhánh
        dfs_L(v, u, w);
        sum += L[v];
    }
    L[u] = min(current_flow, sum);
}

int main() {
    // 1. Đọc input
    // 2. Tìm đường đi từ c1 đến c2 (dùng parent)
    // 3. Đánh dấu các node trên đường
    // 4. Tính L(x) cho mọi node (từ trong ra)
    // 5. Phân loại node: Left, Right, Center
    // 6. Duyệt để tìm max(min(L(u), L(v)))
    return 0;
}

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 100005;
int n, c1, c2;
struct Edge { int to, w; };
vector<Edge> adj[MAXN];
int parent[MAXN];
long long L[MAXN];
bool on_path[MAXN];

void dfs_parent(int u, int p) {
    parent[u] = p;
    for (auto& e : adj[u]) {
        if (e.to != p) dfs_parent(e.to, u);
    }
}

void dfs_L(int u, int p, int limit) {
    long long sum = 0;
    for (auto& e : adj[u]) {
        if (e.to == p || on_path[e.to]) continue;
        dfs_L(e.to, u, e.w);
        sum += L[e.to];
    }
    L[u] = min((long long)limit, sum);
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    if (fopen("highway.in", "r")) freopen("highway.in", "r", stdin);

    cin >> n >> c1 >> c2;
    for (int i=1; i<n; ++i) {
        int u, v, c; cin >> u >> v >> c;
        adj[u].push_back({v, c});
        adj[v].push_back({u, c});
    }

    // 1. Find path c1 -> c2
    dfs_parent(c1, 0);
    vector<int> path;
    for (int u = c2; u != 0; u = parent[u]) path.push_back(u);
    reverse(path.begin(), path.end());
    for (int u : path) on_path[u] = true;

    // 2. Calculate L[u]
    for (int u : path) {
        long long sum = 0;
        for (auto& e : adj[u]) {
            if (on_path[e.to]) continue;
            dfs_L(e.to, u, e.w);
            sum += L[e.to];
        }
        L[u] = sum; // L[c1] and L[c2] are sums of their side branches
    }

    // 3. Solve
    long long ans = 0;
    // Calculate base flow (path c1-c2 capacity)
    long long base_flow = 1e18;
    for (size_t i = 0; i < path.size() - 1; ++i) {
        int u = path[i];
        int v = path[i+1];
        for (auto& e : adj[u]) {
            if (e.to == v) {
                base_flow = min(base_flow, (long long)e.w);
                break;
            }
        }
    }
    ans = base_flow;

    // Collect branches
    vector<long long> left_vals, right_vals;
    vector<vector<long long>> center_branches;

    // Left: branches of c1
    for (auto& e : adj[c1]) {
        if (!on_path[e.to]) left_vals.push_back(L[e.to]);
    }
    // Right: branches of c2
    for (auto& e : adj[c2]) {
        if (!on_path[e.to]) right_vals.push_back(L[e.to]);
    }
    // Center: branches of nodes on path (excluding c1, c2)
    for (size_t i = 1; i < path.size() - 1; ++i) {
        int u = path[i];
        vector<long long> branches;
        for (auto& e : adj[u]) {
            if (!on_path[e.to]) branches.push_back(L[e.to]);
        }
        if (!branches.empty()) center_branches.push_back(branches);
    }

    // Maximize
    // Left + Right
    if (!left_vals.empty() && !right_vals.empty()) {
        ans = max(ans, *max_element(left_vals.begin(), left_vals.end()) + *max_element(right_vals.begin(), right_vals.end()));
    }
    // Left + Left
    if (left_vals.size() >= 2) {
        sort(left_vals.begin(), left_vals.end(), greater<long long>());
        ans = max(ans, left_vals[0] + left_vals[1]);
    }
    // Right + Right
    if (right_vals.size() >= 2) {
        sort(right_vals.begin(), right_vals.end(), greater<long long>());
        ans = max(ans, right_vals[0] + right_vals[1]);
    }
    // Center + Center (same branch)
    for (auto& br : center_branches) {
        if (br.size() >= 2) {
            sort(br.begin(), br.end(), greater<long long>());
            ans = max(ans, br[0] + br[1]);
        }
    }
    // Left + Center (tangent)
    for (auto& br : center_branches) {
        for (long long val : br) {
            if (!left_vals.empty()) ans = max(ans, val + *max_element(left_vals.begin(), left_vals.end()));
            if (!right_vals.empty()) ans = max(ans, val + *max_element(right_vals.begin(), right_vals.end()));
        }
    }

    cout << ans << endl;
    return 0;
}