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

#include <iostream>
#include <vector>
using namespace std;
int const N=5e5+10;
vector<pair<int,int>>nei[N]={};
int ans[N]={};
int dif[N]={};
void dfs(int n)
{
	int mv=-1,dis=1e9+10;
	for (auto [i,w]:nei[n])
	{
		if (ans[i]!=ans[n])
		{
			if (mv==-1)
				mv=i,dis=w;
			if (dis>w)
			{
				mv=i;
				dis=w;
			}
		}
	}
	vector<int>f;
	for (auto [i,w]:nei[n])
	{
		if (ans[i]!=ans[n])
		{
			if (ans[i]==-1)
			{
				ans[i]=1-ans[n];
				f.push_back(i);
			}
		}
	}
	for (auto i:f)
		dfs(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;
	ans[1]=1;
	dfs(1);
	int z=0;
	for (int i=1;i<=n;i++)
		z=max(z,dif[i]);
	cout<<z<<endl;
	for (int i=1;i<=n;i++)
		cout<<(ans[i]==1?'B':'D');
	cout<<endl;
}
int main()
{
    ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
        solve();
}