/*
بسم الله الرحمن الرحيم
Author:
                          (:Muhammad Aneeq:)
*/

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
using namespace std;
#define int long long
int const N=5e5+10;
vector<pair<int,int>>nei[N]={};
int ans[N]={};
int dif[N]={};
void bfs()
{
	set<pair<int,int>>S;
	S.insert({0,1});
	while (S.size())
	{
		auto f=*begin(S);
		S.erase(f);
		if (f.first!=dif[f.second])
			continue;
		for (auto [i,w]:nei[f.second])
		{
			if (ans[i]!=ans[f.second]&&dif[i]>w)
			{
				dif[i]=w;
				ans[i]=1-ans[f.second];
				S.insert({dif[i],i});
			}
			else
			{
				if (f.first<dif[i])
				{
					dif[i]=f.first;
					S.insert({dif[i],i});
				}
			}
		}
	}
}
inline void solve()
{
	int n,m;
	cin>>n>>m;
	while (m--)
	{
		int u,v,w;
		cin>>u>>v>>w;
		nei[u].push_back({v,w});
		nei[v].push_back({u,w});
	}
	for (int i=1;i<=n;i++)
		ans[i]=-1,dif[i]=1e15+10;
	ans[1]=1,dif[1]=0;
	bfs();
	long long w=0;
	for (int i=1;i<=n;i++)
		w=max(w,dif[i]);
	cout<<w<<endl;
	for (int i=1;i<=n;i++)
		cout<<(ans[i]==1?'B':'D');
	cout<<endl;
}
signed main()
{
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
        solve();
}