/*input
4 5
1 2 3
2 3 4
3 4 1
1 4 2
4 2 1
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
//#pragma GCC target("avx2")
//order_of_key #of elements less than x
// find_by_order kth element
using ll=long long;
using ld=long double;
using pii=pair<int,int>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(int i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()),c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll maxn=5e5+5;
const ll maxlg=__lg(maxn)+2;
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=998244353;
const ld PI=acos(-1);
const ld eps=1e-4;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
template<typename T>
ostream& operator<<(ostream& out,vector<T> V){
REP(i,sz(V)) out<<V[i]<<((i!=sz(V)-1)?" ":"\n");
return out;
}
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
out<<P.f<<' '<<P.s;
return out;
}
ll mult(ll a,ll b){
return a*b%MOD;
}
ll mypow(ll a,ll b){
a%=MOD;
if(a==0) return 0;
if(b<=0) return 1;
ll res=1LL;
while(b){
if(b&1) res=(res*a)%MOD;
a=(a*a)%MOD;
b>>=1;
}
return res;
}
vector<pii> v[maxn];
int to[maxn];
int col[maxn];
vector<int> g[maxn];
void dfs(int u){
for(int x:g[u]){
if(!col[x]){
col[x]=3-col[u];
dfs(x);
}
}
}
int main(){
ios::sync_with_stdio(false),cin.tie(0);
int n,m;
cin>>n>>m;
REP(i,m){
int a,b,w;
cin>>a>>b>>w;
v[a].pb({w,b});
v[b].pb({w,a});
}
ll ans=0;
vector<int> st;
REP1(i,n){
sort(ALL(v[i]));
MXTO(ans,v[i][0].f);
to[i]=v[i][0].s;
if(to[v[i][0].s]==i) continue;
g[i].pb(v[i][0].s);
g[v[i][0].s].pb(i);
}
cout<<ans<<'\n';
REP1(i,n){
if(!col[i]){
col[i]=1;
dfs(i);
}
if(col[i]==1) cout<<'B';
else cout<<'D';
}
}
