#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;
vector<pii> adj[N + 5];
int total, min_w, node;
int color[N + 5];
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 <= m; i++)
{
int u, v, w;
cin >> u >> v >> w;
adj[u].push_back({v, w});
adj[v].push_back({u, w});
}
for(int i = 1; i <= n; i++)
{
if(color[i]) continue;
min_w = inf;
for(auto it : adj[i])
if(it.se < min_w)
{
min_w = it.se;
node = it.fi;
}
total = max(total, min_w);
if(color[node] != 0) color[i] = 3 - color[node];
else {
color[i] = 1;
color[node] = 3 - color[i];
}
}
cout << total << el;
for(int i = 1; i <= n; i++)
cout << (color[i] == 1 ? 'D' : 'B');
return 0;
}
