#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

struct edge {
    int u, v, w;
};
bool cmp(const edge &a, const edge &b) {
    return a.w < b.w;
}

#define N 500010

int cha[N], hang[N];

int find(int u) {
    if (cha[u] != u) cha[u] = find(cha[u]);
    return cha[u];
}

bool join(int u, int v) {
    u = find(u); v = find(v);
    if (u == v) return false;
    if (hang[u] == hang[v]) hang[u]++;
    if (hang[u] < hang[v]) cha[u] = v;
    else cha[v]=u;
    return true;
}

void dfs(vector<vector<int>> &adj, int u, vector<int> &visited, int color){
    if(visited[u]) return;
    visited[u]= color;
    int new_color= (color==1)? 2 : 1;
    for(auto &v: adj[u]){
        dfs(adj, v, visited, new_color);
    }
}

int main() {
    ios::sync_with_stdio(false); cin.tie(0);

    int n, m; cin >> n >> m;

    vector<edge> edges(m);
    for (edge &e: edges) cin >> e.u >> e.v >> e.w;

    sort(edges.begin(), edges.end(), cmp);

    for (int i=1; i<=n; i++) {
        cha[i] = i;
        hang[i] = 0;
    }


    int ans= 0;
    vector<vector<int>> adj(n+1);
    vector<int> visited(n+1);
    for (edge &e: edges) {
        if (join(e.u, e.v)) {
            adj[e.u].push_back(e.v);
            adj[e.v].push_back(e.u);
            ans= max(ans, e.w);
        }
    }

    cout << ans << "\n";
    for(int i= 1; i<= n; i++){
        if(!visited[i]){
            dfs(adj, i, visited, 1);
        }
        if(visited[i]== 1){
            cout << 'B';
        }
        else {
            cout << 'D';
        }
    }
    return 0;
}