#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define pb push_back
#define f(i, a, b) for(int i = a; i <= b; i++)
#define fi first
#define se second
#define mll map<ll, ll>
#define sll set<ll>
const ll du = 1e9 + 7;
const ll ars = 1e6 + 5;
// 1
int n, m;
int c[ars], num[ars];
vector<pll> adj[ars];
struct edge{
ll u, v, w;
};
edge e[ars];
bool cmp(edge a, edge b){
return a.w < b.w;
}
ll timcha(int a){
while(a != c[a]) a = c[a];
return a;
}
bool dsu(int x, int y){
x = timcha(x);
y = timcha(y);
if(x == y) return false;
if(num[x] > num[y]) swap(x, y);
c[x] = y;
num[y] += num[x];
return true;
}
void mst(){
for(int i = 1; i <= n; i++){
num[i] = 1;
c[i] = i;
}
sort(e + 1, e + 1 + m, cmp);
int dem = 0;
for(int i = 1; i <= m; i++){
if(dem == (n - 1)) break;
bool fl = dsu(e[i].u, e[i].v);
if(fl == false) continue;
auto[u, v, w] = e[i];
adj[u].pb({v, w});
adj[v].pb({u, w});
dem++;
}
}
char res[ars];
void dfs(int u, int p, bool f){
if(f) res[u] = 'D';
else res[u] = 'B';
for(auto[v, w] : adj[u]){
if(v == p) continue;
dfs(v, u, !f);
}
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define task "tenshi"
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
cin >> n >> m;
for(int i = 1; i <= m; i++){
cin >> e[i].u >> e[i].v >> e[i].w;
}
mst();
ll ans = 0;
for(int i = 1; i <= n; i++){
ll mn = 1e18;
for(auto[v, w] : adj[i]){
//cout << i << " " << v << '\n';
mn = min(mn, w);
}
if(mn != 1e18)
ans = max(ans, mn);
}
cout << ans << '\n';
dfs(1, 0, 0);
for(int i = 1; i <= n; i++) cout << res[i];
}
