#include <bits/stdc++.h>
#define N 500000
#define ll long long
#define MOD 1000000007
#define inf 2000000000
#define llf 1000000000000000000
// #define base 31
#define MASK(i) (1 << (i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define fi first
#define se second
#define el '\n'
using namespace std;
int n, m;
int total;
int min_w[N + 5], nei[N + 5], color[N + 5];
vector<int> g[N + 5];
struct Edge{
int u, v, w;
} edges;
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
// freopen(".INP", "r", stdin);
// freopen(".OUT", "w", stdout);
cin >> n >> m;
for(int i = 1; i <= n; i++)
{
min_w[i] = inf;
color[i] = -1;
}
for(int i = 0; i < m; i++)
{
int u, v, w;
cin >> u >> v >> w;
if(u == v) continue;
if(w < min_w[u])
{
min_w[u] = w;
nei[u] = v;
}
if(w < min_w[v])
{
min_w[v] = w;
nei[v] = u;
}
}
for(int i = 1; i <= n; i++)
if(min_w[i] != inf) total = max(total, min_w[i]);
for(int i = 1; i <= n; i++)
if(nei[i] != 0)
{
int u = i;
int v = nei[i];
g[u].push_back(v);
g[v].push_back(u);
}
for(int i = 1; i <= n; i++)
if(color[i] == -1)
{
queue<int> q;
q.push(i);
color[i] = 0;
while(q.size())
{
int u = q.front(); q.pop();
for(int v : g[u])
if(color[v] == -1)
{
color[v] = 1 - color[u];
q.push(v);
}
}
}
cout << total << el;
for(int i = 1; i <= n; i++)
cout << (color[i] == 0 ? 'B' : 'D');
return 0;
}
