#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define N 500005
#define ii pair<int,int>
#define bit(i,j) ((i>>j)&1)
#define sz(i) (int)i.size()
#define endl '\n'
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
using namespace std;
int n, m;
struct arr
{
    int u, v, w;
};
vector<arr>vec;
namespace sub1
{
int res;
int c[N], par[N], sz[N];
vector<ii>g[N];
bool cmp(arr a, arr b)
{
    return a.w < b.w;
}
void init()
{
    for(int i = 1; i <= n; i++)
    {
        par[i] = i;
        sz[i] = 1;
    }
}
int found(int v)
{
    if(v == par[v])
        return v;
    return par[v] = found(par[v]);
}
bool union_set(int u, int v)
{
    u = found(u);
    v = found(v);
    if(u == v)
        return 0;
    if(sz[u] > sz[v])
        swap(u, v);
    par[v] = u;
    sz[u] += sz[v];
    return 1;
}
void kruskal()
{
    sort(vec.begin(), vec.end(), cmp);
    for(int i = 0; i < sz(vec); i++)
    {
        int u = vec[i].u, v = vec[i].v, w = vec[i].w;
        if(union_set(u, v))
        {
            g[u].push_back({v, w});
            g[v].push_back({u, w});
        }
    }
}
void dfs(int u, int p)
{
    int ans = INT_MAX;
    c[u] = c[p] ^ 1;
    for(ii i : g[u])
    {
        int v = i.F, w = i.S;
        if(v == p)
            continue;
        ans = min(ans, w);
        dfs(v, u);
    }
    if(ans!=INT_MAX)
        res = max(res, ans);
}
void solve()
{
    init();
    kruskal();
    c[1] = 1;
    dfs(1, 0);
    cout << res << endl;
    for(int i = 1; i <= n; i++)
        if(c[i])
            cout << "B";
        else
            cout << "D";
}
}
main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    for(int i = 1; i <= m; i++)
    {
        int x, y, z;
        cin >> x >> y >> z;
        vec.push_back({x, y, z});
    }
    sub1::solve();
}
/**
3 3
1 2 3
2 3 1
1 3 2
**/