#include <bits/stdc++.h>

using i64 = long long;
struct DSU {
    std::vector<int> f, siz;
    
    DSU() {}
    DSU(int n) {
        init(n);
    }
    
    void init(int n) {
        f.resize(n);
        std::iota(f.begin(), f.end(), 0);
        siz.assign(n, 1);
    }
    
    int find(int x) {
        while (x != f[x]) {
            x = f[x] = f[f[x]];
        }
        return x;
    }
    
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    
    bool merge(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) {
            return false;
        }
        siz[x] += siz[y];
        f[y] = x;
        return true;
    }
    
    int size(int x) {
        return siz[find(x)];
    }
};
int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int n, m;
    std::cin >> n >> m;
    
    std::vector<int> u(m), v(m), w(m);
    for (int i = 0; i < m; i++) {
        std::cin >> u[i] >> v[i] >> w[i];
        u[i]--;
        v[i]--;
    }
    
    std::vector<int> p(m);
    std::iota(p.begin(), p.end(), 0);
    std::sort(p.begin(), p.end(),
        [&](int i, int j) {
            return w[i] < w[j];
        });
    
    DSU dsu(n);
    int ans = 0;
    std::vector<int> deg(n);
    std::vector<std::vector<int>> adj(n);
    for (auto i : p) {
        if (dsu.merge(u[i], v[i])) {
            if (deg[u[i]]++ == 0 || deg[v[i]]++ == 0) {
                ans = w[i];
            }
            adj[u[i]].push_back(v[i]);
            adj[v[i]].push_back(u[i]);
        }
    }
    
    std::cout << ans << "\n";
    std::vector<int> d(n);
    auto dfs = [&](auto &&self, int x, int p) -> void {
        for (auto y : adj[x]) {
            if (y == p) {
                continue;
            }
            d[y] = d[x] ^ 1;
            self(self, y, x);
        }
    };
    dfs(dfs, 0, -1);
    
    for (int i = 0; i < n; i++) {
        std::cout << "BD"[d[i]];
    }
    std::cout << "\n";
    
    return 0;
}