#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=5e5+10;
const int P=17;
const int inf=1e18;
int dist[P][P],dp[N];
vector<pair<int,int>> ma[N];
bool vis[N];
char ans1[N];
bool cal[N];
void dfs(int x,char c='B')
{
	vis[x]=1;
	ans1[x]=c;
	if(c=='B')
		c='D';
	else
		c='B';
	for(auto [w,y]:ma[x])
	{
		if(!vis[y])
		{
			dfs(y,c);
		}
	}
}
void dfs_(int x){
	cal[x]=1;
	for(auto [w,y]:ma[x])
	{
		if(!cal[y])
			dfs_(y);
		if(ans1[x]!=ans1[y])
		{
			dp[x]=min(dp[x],w);
		}
		else{
			dp[x]=min(dp[x],dp[y]+w);
		}
	}
}
signed main()
{
	srand(time(0));
	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({c,y});
		ma[y].push_back({c,x});
	}
	for(int i=1;i<=n;i++)
		sort(begin(ma[i]),end(ma[i]));
	dfs(1);
	int ans=0;
	for(int v=1;v<=n;v++)
		dp[v]=inf;
	dfs_(1);
	for(int v=1;v<=n;v++)
		ans=max(ans,dp[v]);
	int val=ans,val1;
	string ap,ap1;
	for(int j=1;j<=n;j++)
		ap+=ans1[j];
	cout<<val<<endl;
	cout<<ap<<endl;
	return 0;
}