#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> ii;
typedef vector<ii> vi;

void dijkstra(const vector<vi> &adj)
{
    priority_queue<ii, vector<ii>, greater<>> pq;
    vector<int> dist(adj.size(), INT_MAX);
    pq.emplace(0, 0);
    dist[0] = 0;
    vector<int> parent(adj.size(), -1);

    while (!pq.empty())
    {
        auto [d, u] = pq.top();
        pq.pop();
        if (d > dist[u])
            continue;
        for (auto [v, w] : adj[u])
        {
            if (max(dist[u], w) < dist[v])
            {
                dist[v] = max(dist[u], w);
                pq.emplace(dist[v], v);
                parent[v] = u;
            }
        }
    }
    const int max_cost = *ranges::max_element(dist);
    vector<vector<int>> adj2(adj.size());
    for(int i= 0; i < adj.size(); i++)
    {
        int u = i;
        if(int v = parent[i]; v != -1)
        {
            adj2[u].emplace_back(v);
            adj2[v].emplace_back(u);
        }
    }
    vector<int> visited(adj.size());
    function<void(int, int)> dfs = [&](const int u, const int color)
    {
        visited[u] = color;
        for(const int v : adj2[u])
        {
            if(!visited[v])
            {
                dfs(v, (color==1)? 2 : 1);
            }
        }
    };
    dfs(0, 1);
    cout << max_cost << '\n';
    for(int i = 0; i < adj.size(); i++)
    {
        if(visited[i] == 1)
        {
            cout << 'D';
        }
        else
        {
            cout << 'B';
        }
    }
}

int main()
{
    ios::sync_with_stdio(false), cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    vector<vi> adj(n);
    for (int i = 0; i < m; i++)
    {
        int u, v, w;
        cin >> u >> v >> w;
        u--, v--;
        adj[u].emplace_back(v, w);
        adj[v].emplace_back(u, w);
    }
    dijkstra(adj);
    return 0;

}