#include <bits/stdc++.h>

namespace IO {
	template <class Stream>
	void write_int128(Stream& out, __int128 v) {
		if (v >= 10) {
			write_int128(out, v / 10);
		}
		out << (int) (v % 10);
	}

	template <class Stream>
	Stream& fmtbase(Stream& out, const char* format) {
		for (; *format; format++) {
			if (*format == '{' && *(format + 1) == '}') {
				throw std::invalid_argument("Error Number of Parameters!");
			}
			
			out << *format;
		}
		
		return out;
	}
	
	template <class Stream, class... Nxt>
	Stream& fmtbase(Stream& out, const char* format, const __int128& value, const Nxt&... nxt) {
		for (; *format; format++) {
			if (*format == '{' && *(format + 1) == '}') {
				write_int128(out, value);
				return fmtbase(out, format + 2, nxt...);
			} 
			
			out << *format;
		}
		
		throw std::invalid_argument("Error Number of Parameters!");
	}

	template <class Stream, class Fst, class... Nxt>
	Stream& fmtbase(Stream& out, const char* format, const Fst& value, const Nxt&... nxt) {
		for (; *format; format++) {
			if (*format == '{' && *(format + 1) == '}') {
				out << value;
				return fmtbase(out, format + 2, nxt...);
			} 
			
			out << *format;
		}
		
		throw std::invalid_argument("Error Number of Parameters!");
	}
	
	template <class... Ps>
	std::string to_string(const char* format, const Ps&... ps) {
		std::stringstream ss;
		fmtbase(ss, format, ps...);
		return ss.str();
	}

	template <class... Ps>
	std::ostream& fmtout(const char* format, const Ps&... ps) {
		return fmtbase(std::cout, format, ps...);
	}
	
	template <class... Ps>
	std::ostream& fmterr(const char* format, const Ps&... ps) {
		return fmtbase(std::cerr, format, ps...);
	}
	
	std::istream& allin() {
		return std::cin;
	}
	
	template <class Fst, class ... Nxt>
	std::istream& allin(Fst& fst, Nxt&... nxt) {
		std::cin >> fst;
		return allin(nxt...);
	}
	
	template <class Iter>
	std::istream& rangin(Iter begin, Iter end) {
		while (begin != end) {
			std::cin >> *begin;
			begin++;
		}
		
		return std::cin;
	}
	
	namespace Fast {
		bool sync = false;
		
		char buf[1 << 23];
		char *p1 = buf, *p2 = buf;
		
		void sync_with_ios(bool s) {
			sync = s;
		}
		
		inline char getchar() {
			if (sync) {
				return (char) std::cin.get();
			}
			else {
				return (p1 == p2) && (p2 = (p1 = buf) + fread(buf, 1, 1 << 22, stdin)), p1 == p2 ? EOF : *p1++;
			}
		}
		
		void read() { }
		
		template <class T, class... U>
		void read(T& x, U&... us) {
			x = 0;
			T pos = 1;
			
			char c = getchar();
			while (!isdigit(c)) {
				if (c == '-') {
					pos = -1;
				}
				
				c = getchar();
			}
			
			while (isdigit(c)) {
				x = 10 * x + c - '0';
				c = getchar();
			}
			
			x *= pos;
			read(us...);
		}
		
		template <class T>
		void write(const T& t) {
			if (t > 10) {
				write(t / 10);
			}
			
			std::cout << (int) (t % 10);
		}
	}
}

namespace Solve {
	#define int long long

	using namespace IO;

	using ll = long long;
	using ul = unsigned long long;
	using db = double;
	using ld = long double;
	using ui = unsigned;
	using ib = __int128;
	using ub = __uint128_t;

	int const INF = std::numeric_limits<int>::max();
	int const NINF = std::numeric_limits<int>::min();
	ll const LINF = std::numeric_limits<ll>::max();
	ll const LNINF = std::numeric_limits<ll>::min();
	ld const EPS = 1e-8;

	std::mt19937_64 mt;

	ll rnd(ll l, ll r) {
		return std::uniform_int_distribution<ll>(l, r)(mt);
	}

	template <class T>
	inline int isz(const T& v) {
		return v.size();
	}

	template <class T>
	inline T& ckmx(T& a, T b) {
		return a < b ? (a = b) : a;
	}

	template <class T>
	inline T& ckmi(T& a, T b) {
		return b < a ? (a = b) : a;
	}

	int const N = 5e5 + 10;

	struct Edge {
		int x, y, w;
	};

	struct Node {
		int x, v;
	};

	std::vector<Node> tr[N + 1];
	int fa[N + 1];
	Edge eds[N + 1];
	int n, m;
	int ans;
	int dep[N + 1];

	int get(int x) {
		return fa[x] == x ? x : fa[x] = get(fa[x]);
	}

	void dfs(int x, int fa) {
		dep[x] = dep[fa] + 1;
		int mi = INF;
		for (auto& to : tr[x]) {
			ckmi(mi, to.v);
			if (to.x != fa) {
				dfs(to.x, x);
			}
		}
		ckmx(ans, mi);
	}

	void main() {
		std::cin >> n >> m;
		for (int i = 1; i <= m; i++) {
			std::cin >> eds[i].x >> eds[i].y >> eds[i].w;
		}

		std::sort(eds + 1, eds + m + 1, [&](const Edge& a, const Edge& b) {
			return a.w < b.w;
		});

		for (int i = 1; i <= n; i++) {
			fa[i] = i;
		}

		for (int i = 1; i <= m; i++) {
			int x = get(eds[i].x);
			int y = get(eds[i].y);
			if (x != y) {
				tr[x].push_back({ y, eds[i].w });
				tr[y].push_back({ x, eds[i].w });
				fa[x] = y;
			}
		}

		dfs(1, 0);
		fmtout("{}\n", ans);
		for (int i = 1; i <= n; i++) {
			fmtout("{}", dep[i] % 2 ? "B" : "D");
		}
		fmtout("\n");
	}

	void init() {
		
	}

	void clear() {

	}
}

signed main() {
#ifndef ONLINE_JUDGE
	auto input_file = freopen("d.in", "r", stdin);
	auto output_file = freopen("d.out", "w", stdout);
#endif

	auto seed = std::chrono::high_resolution_clock::now().time_since_epoch().count();

	IO::fmterr("seed: {}\n", seed);
	Solve::mt.seed(seed);

	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	std::cout.tie(0);

	int t = 1;
	// std::cin >> t;

	Solve::init();

	for (int id = 1; id <= t; id++) {
		Solve::main();
		Solve::clear();
	}

#ifndef ONLINE_JUDGE
	std::cout.flush();
	fclose(input_file);
	fclose(output_file);
#endif

	return 0;
}