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#include <bits/stdc++.h> // Tomasz Nowak
using namespace std;     // XIII LO Szczecin
using LL = long long;    // Poland
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int n, m, a, b;
	cin >> n >> m >> a >> b;
	assert(a + b <= n);

	vector<vector<int>> graph(n);
	while(m --> 0) {
		int v, u;
		string mid;
		cin >> v >> mid >> u;
		--v, --u;
		if(mid == "--") {
			graph[v].emplace_back(u);
			graph[u].emplace_back(v);
		}
		else if(mid == "->")
			graph[v].emplace_back(u);
	}

	vector<int> vis(a);
	REP(i, a) {
		vector<bool> visited(n, false);
		vis[i] = true;
		deque<int> que = {i};

		while(not que.empty()) {
			int v = que.front();
			que.pop_front();
			for(int u : graph[v])
				if(not visited[u]) {
					visited[u] = true;
					que.emplace_back(u);
				}
		}

		int mask = 0;
		FOR(v, a, a + b - 1)
			if(visited[v])
				mask |= 1 << (v - a);
		vis[i] = mask;
	}

	int answer = 0;
	REP(mask, (1 << b)) {
		bool good = true;
		REP(v, a)
			if((vis[v] & mask) == 0) {
				good = false;
				break;
			}
		answer += good;
	}
	cout << answer << '\n';
}