#include <bits/stdc++.h>
#define ll              long long
#define pii             pair<int,int>
#define pll             pair<ll,ll>
#define rep(i,m,n)      for(int i=(m); i<=(n); i++)
#define reb(i,m,n)      for(int i=(m); i>=(n); i--)
#define iter(id, v)     for(auto id : v)
#define fs              first
#define se              second
#define MP              make_pair
#define pb              push_back
#define bit(msk, i)     ((msk >> i) & 1)
#define SZ(v)           (ll)v.size()
#define ALL(v)          v.begin(),v.end()

using namespace std;

mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }

const int N = 2e5 + 7;
const int Mod = 1e9 + 2022; ///loonf mod sai
const int INF = 1e9;
const ll BASE = 137;
const int szBL = 320;

struct Disjoint_set {
    int lab[N], sz[N];
    void init (int n) {
        rep (i, 1, n) {
            lab[i]= i, sz[i] = 1;
        }
    }

    int Find (int u) {
        return u == lab[u] ? u : lab[u] = Find(lab[u]);
    }

    bool Join (int u, int v){
        u = Find(u);
        v = Find(v);
        if (u == v) return 0;
        if (sz[u] < sz[v]) swap(u, v);
        lab[v] = u;
        sz[u] += sz[v];
        return 1;
    }
}DSU;

struct Edge {
    int u, v, w;
};
int n, m;
vector<Edge> edges;
vector<int> ke[N];

bool dd[N];

void dfs (int u, int p) {
    iter (&v, ke[u]) {
        if (v != p) {
            dd[v] = dd[u] ^ 1;
            dfs(v, u);
        }
    }
}

void solution() {
    cin >> n >> m;
    rep (i, 1, m) {
        int u, v, w;
        cin >> u >> v >> w;
        edges.pb({u, v, w});
    }
    DSU.init(n);
    sort(ALL(edges), [] (Edge A, Edge B) { return A.w < B.w; });
    int mx = 0;
    iter (&id, edges) {
        if (DSU.Join(id.u, id.v)) {
            mx = id.w;
            ke[id.u].pb(id.v);
            ke[id.v].pb(id.u);
        }
    }
    cout << mx <<"\n";
    dfs(1, 0);
    rep (i, 1, n) cout << (dd[i] == 0 ? 'D' : 'B');

}

#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
//    file("c");
    ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
    int num_Test = 1;
//    cin >> num_Test;
    while (num_Test--)
        solution();
}
/*
no bug +8
chu y break hay return se lam hong logic
xet transition cua i va i + 1
construct ket qua
chu y truong hop : KHONG CO GI

ko làm được

hướng 1: đổi hướng làm
hướng 2: đưa ra nhận xét

tim mo hinh bai toan sau khi doc de

trung ten bien trong ham gan nhat co the dan den sai

10 7 3
6 5
3 6
9 3
8 3
7 8
7 1
2 5
7 10
8 4
9 4 10 1 10 7 6
4 4
1 3
6 7



*/