#include<bits/stdc++.h>
using namespace std;
#define fi first
#define sc second
#define pii pair<int,int>
#define pb push_back
#define umap unordered_map
#define mset multiset
#define pq priority_queue
#define ull unsigned long long
#define i128 __int128
const int maxn=5e5+10;
int n,m,vis[maxn],col[maxn];
pii minn[maxn];
void dfs(int u){
    vis[u]=1;
    if(!vis[minn[u].sc]){
        col[minn[u].sc]=(!col[u]);
        dfs(minn[u].sc);
    }
}
void solve(){
    cin>>n>>m;
    for(int i=1;i<=n;i++) minn[i]={1e9,0};
    for(int i=1,u,v,w;i<=m;i++){
        cin>>u>>v>>w;
        minn[u]=min(minn[u],{w,v});
        minn[v]=min(minn[v],{w,u});
    }dfs(1);
    cout<<(*max_element(minn+1,minn+n+1)).fi<<endl;
    for(int i=1;i<=n;i++) cout<<(col[i]?"B":"D");
    cout<<endl;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--) solve();
    return 0;
}
/*
Samples
input:

output:

THINGS TODO:
检查freopen，尤其是后缀名
检查空间
检查调试语句是否全部注释
*/