#include <bits/stdc++.h>

using namespace std;

#define int long long
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()

const int M = 5e5, inf = 1e9+1;

int dep[M],col[M],sz[M];
vector<int> ver[M],nei[M];

bool add(int u,int v)
{
	if (col[u]==col[v])
		return false;
	if (sz[col[u]]>sz[col[v]])
		swap(u,v);
	int x=col[u];
	for (int i:ver[x])
	{
		col[i]=col[v];
		ver[col[v]].push_back(i);
		sz[col[v]]++;
		sz[x]--;
	}
	ver[x].clear();
	return true;
}

void dfs(int u,int p=-1)
{
	for (int i:nei[u])
		if (i!=p)
		{
			dep[i]=1-dep[u];
			dfs(i,u);
		}
}

signed main()
{
	int n,m;
	cin>>n>>m;
	int ans[n];
	for (int i=0;i<n;i++)
	{
		ans[i]=inf;
		col[i]=i,sz[i]=1;
		ver[i]={i};
	}
	vector<pair<int,pair<int,int>>> edg;
	for (int i=0;i<m;i++)
	{
		int u,v,w;
		cin>>u>>v>>w;
		u--,v--;
		ans[u]=min(ans[u],w);
		ans[v]=min(ans[v],w);
		edg.push_back({w,{u,v}});
	}
	int mx=ans[0];
	for (int i=1;i<n;i++)
		mx=max(mx,ans[i]);
	sort(all(edg));
	for (int i=0;i<m;i++)
	{
		int u=edg[i].second.first,v=edg[i].second.second;
		if (add(u,v))
		{
			nei[u].push_back(v);
			nei[v].push_back(u);
		}
	}
	dfs(0);
	cout<<mx<<endl;
	for (int i=0;i<n;i++)
		if (dep[i])
			cout<<'D';
		else
			cout<<'B';
	cout<<endl;
	
	return 0;
}