#include <bits/stdc++.h>
#define ent '\n'
#define f first
#define s second
#define int long long

using namespace std;
typedef long long ll;
const int maxn = 1e6 + 12;
const int mod = 1e9 + 7;

vector<pair<int, int>> g[maxn];
bool col[maxn];
int dp[maxn];
int p[maxn];
int a[maxn];
int b[maxn];
int n, m, s;

int get(int x){
    if(p[x] == x) return x;
    return p[x] = get(p[x]);
}

void dfs(int v, int p){
    dp[v] = 0;
    if(g[v].size() == 1 && p != 0){
        dp[v] = 1e18;
    }
    for(auto [to, w]:g[v]){
        if(to != p){
            dfs(to, v);
            int x = max(w, dp[to]), y = w;
            for(auto [u, c]:g[to]){
                if(u != v) {
                    y = max(y, dp[u]);
                }
            }
            if(g[to].size() == 1) {
                y = 1e18;
                x = w;
            }
            dp[v] = max(dp[v], min(x, y));
        }
    }
}

void calc(int v, int p, int c){
    col[v] = c;
    for(auto [to, w]:g[v]){
        if(to != p){
            int x = max(w, dp[to]), y = w;
            for(auto [u, c]:g[to]){
                if(u != v) {
                    y = max(y, dp[u]);
                }
            }
            if(g[to].size() == 1) {
                y = 1e18;
                x = w;
            }
            if(x <= y){
                calc(to, v, 1-c);
            }
            else{
                calc(to, v, c);
            }
        }
    }
}

void solve(){
    cin >> n >> m;
    for(int i=1;i<=n;i++){
        p[i] = i;
    }
    vector<pair<int, pair<int, int>>> v;
    while(m--){
        int a, b, c;
        cin >> a >> b >> c;
        v.push_back({c, {a, b}});
    }
    int ans = 0;
    sort(v.begin(), v.end());
    for(auto [w, t]:v){
        auto [x, y] = t;
        if(get(x) != get(y)){
            p[get(x)] = get(y);
            g[x].push_back({y, w});
            g[y].push_back({x, w});
            ans = max(ans, w);
        }
    }
    dfs(1, 0);
    calc(1, 0, 0);
    cout << dp[1] << ent;
    for(int i=1;i<=n;i++){
        if(col[i]) cout << 'D';
        else cout << 'B';
    }
}

signed main(){
    srand(time(0));
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t = 1;
    // cin >> t;
    while(t--){
        solve();
    }
}