# include <bits/stdc++.h>
using namespace std;
const int MN = 201;
vector <pair <int, char> > opening[MN];
vector <pair <int, char> > closing[MN];
char val[128];
typedef long long res_t;
res_t dp[MN][MN];
const res_t inf = 1e18;
set <pair <res_t, pair <int, int> > > dijkstra_queue;
void enque(int start, int end, res_t value) {
if (dp[start][end] > value) {
dijkstra_queue.erase(make_pair(dp[start][end], make_pair(start, end)));
dp[start][end] = value;
dijkstra_queue.insert(make_pair(dp[start][end], make_pair(start, end)));
}
}
int main() {
val['['] = 1;
val[']'] = -1;
val['{'] = 2;
val['}'] = -2;
val['('] = 3;
val[')'] = -3;
val['<'] = 4;
val['>'] = -4;
int n, m, s, t;
scanf("%d%d%d%d", &n, &m, &s, &t);
fprintf(stderr, "n = %d m = %d\n", n, m);
for (int i = 0; i < m; ++i) {
int a, b;
char c;
scanf("%d%d %c", &a, &b, &c);
c = val[(int)c];
if (c > 0)
opening[b].push_back(make_pair(a, c));
else
closing[a].push_back(make_pair(b, -c));
}
for (int i = 1; i <= n; ++i)
for (int k = 1; k <= n; ++k)
dp[i][k] = inf;
for (int i = 1; i <= n; ++i)
enque(i, i, 0);
int turns = 0;
while (dijkstra_queue.size()) {
turns++;
auto curr = *dijkstra_queue.begin();
dijkstra_queue.erase(dijkstra_queue.begin());
int start = curr.second.first, end = curr.second.second;
assert(dp[start][end] < inf);
for (int i = 1; i <= n; ++i) {
enque(start, i, dp[start][end] + dp[end][i]);
enque(i, end, dp[i][start] + dp[start][end]);
}
for (auto x : opening[start])
for (auto y : closing[end]) {
if (x.second == y.second)
enque(x.first, y.first, dp[start][end] + 2);
}
}
fprintf(stderr, "%d / %d turns\n", turns, n * n);
if (dp[s][t] == inf) {
printf("-1\n");
fprintf(stderr, "-1\n");
}
else {
printf("%lld\n", dp[s][t]);
fprintf(stderr, "%lld = %.3Le\n", dp[s][t], (long double)dp[s][t]);
}
}
