#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=5e5+10;
const int P=17;
int dist[P][P];
vector<pair<int,int>> ma[N];
bool vis[N];
char ans1[N];
void dfs(int x,char c='B')
{
	vis[x]=1;
	ans1[x]=c;
	if(c=='B')
		c='D';
	else
		c='B';
	for(auto [y,w]:ma[x])
	{
		if(!vis[y])
		{
			dfs(y,c);
		}
	}
}
void compute(int n)
{
	for(int st=1;st<=n;st++)
	{
		for(int ot=1;ot<=n;ot++)
			dist[st][ot]=1e11;
		dist[st][st]=0;
		priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> pq;
		pq.push({0,st});
		while(pq.size())
		{
			auto it=pq.top();
			pq.pop();
			if(dist[st][it.second]==it.first)
			{
				for(auto [nxt,wei]:ma[it.second])
				{
					if(dist[st][nxt]>(wei+it.first))
					{
						dist[st][nxt]=wei+it.first;
						pq.push({dist[st][nxt],nxt});
					}
				}
			}
		}
	}
}
signed main()
{
	int n,m;
	cin>>n>>m;
	for(int j=0;j<m;j++)
	{
		int x,y,c;
		cin>>x>>y>>c;
		ma[x].push_back({y,c});
		ma[y].push_back({x,c});
	}
	if(n<=16)
	{
		compute(n);
		// full brute forcess
		int val=1e11;
		string an="";
		for(int mask=0;mask<(1<<n);mask++)
		{
			string ans;
			for(int l=0;l<n;l++)
			{
				if(mask&(1<<l))
				{
					ans+="B";
				}
				else{
					ans+="D";
				}
			}
			int cur=0;
			for(int st=1;st<=n;st++)
			{

				int D=1e11,B=1e11;
				for(int ot=1;ot<=n;ot++)
				{
					if(ans[ot-1]=='B')
					{
						B=min(B,dist[st][ot]);
					}
					else
					{
						D=min(D,dist[st][ot]);
					}
				}
				cur=max(cur,max(B,D));
			}
			if(cur<val)
			{
				val=cur;
				an=ans;
			}
		}
		cout<<val<<endl;
		cout<<an<<endl;
	}
	else
	{
		/*
			Lets think about DP
			mb the dp is like this dp[i][2] = in the subtree of i
		*/
		dfs(1);
		cout<<1<<endl;
		for(int j=1;j<=n;j++)
			cout<<ans1[j];
		cout<<endl;
	}
	return 0;
}