#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
void DBG() { cerr << "]" << endl; }
template<class H, class... T> void DBG(H h, T... t) { cerr << to_string(h); if(sizeof...(t)) cerr << ", "; DBG(t...); }
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)

const int N = 203;
const ll inf = 2e18;
vector<pair<int, char>> in[N], out[N];
ll d[N][N];

bool match(char a, char b) {
    if (a == '(') return (b == ')');
    if (a == '{') return (b == '}');
    if (a == '<') return (b == '>');
    if (a == '[') return (b == ']');
    return false;
}


void solve() {
   int n, m, s, t; cin >> n >> m >> s >> t;
   for (int i = 0; i <= n; i++)
        for (int j = 0; j <= n; j++)
            if (i != j) d[i][j] = inf;

   for (int i = 0; i < m; i++) {
        int u, v; char c;
        cin >> u >> v >> c;
        in[v].push_back({u, c});
        out[u].push_back({v, c});
   }
   priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>, greater<>> pq;
   for (int i = 1; i <= n; i++) pq.emplace(0, i, i);

   while (!pq.empty()) {
        auto [w, u, v] = pq.top(); pq.pop();
        if (d[u][v] != w) continue;
        for (auto [pu, c1] : in[u]) {
            for (auto [pv, c2] : out[v]) {
                if (match(c1, c2)) {
                    if (w+2 < d[pu][pv]) {
                        d[pu][pv] = w+2;
                        pq.emplace(d[pu][pv], pu, pv);
                    }
                }
            }
        }

        for (int x = 1; x <= n; x++) {
            for (int y = 1; y <= n; y++) {
                if (d[x][y] > d[x][u]+d[u][v]+d[v][y]) {
                    d[x][y] = d[x][u]+d[u][v]+d[v][y];
                    pq.emplace(d[x][y], x, y);
                }
            }
        }
   }

   cout << (d[s][t] == inf ? -1 : d[s][t]) << "\n";
}
signed main() {
    ios::sync_with_stdio(false); cin.tie(0);
	int t=1; //cin >> t;
	while (t--) {
        solve();
	}
}