#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define N 200
#define INF 0x3f3f3f3f3f3f3f3fLL
void append(int **ej, int **ec, int *eo, int i, int j, int c) {
int o = eo[i]++;
if (o >= 2 && (o & o - 1) == 0) {
ej[i] = (int *) realloc(ej[i], o * 2 * sizeof *ej[i]);
ec[i] = (int *) realloc(ec[i], o * 2 * sizeof *ec[i]);
}
ej[i][o] = j, ec[i][o] = c;
}
long long dd[N * N]; int iq[N * N + 1], pq[N * N], cnt;
int lt(int i, int j) { return dd[i] < dd[j]; }
int p2(int p) {
return (p *= 2) > cnt ? 0 : (p < cnt && lt(iq[p + 1], iq[p]) ? p + 1 : p);
}
void pq_up(int i) {
int p, q, j;
for (p = pq[i]; (q = p / 2) && lt(i, j = iq[q]); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_dn(int i) {
int p, q, j;
for (p = pq[i]; (q = p2(p)) && lt(j = iq[q], i); p = q)
iq[pq[j] = p] = j;
iq[pq[i] = p] = i;
}
void pq_add_last(int i) {
iq[pq[i] = ++cnt] = i;
}
int pq_remove_first() {
int i = iq[1], j = iq[cnt--];
if (j != i)
pq[j] = 1, pq_dn(j);
pq[i] = 0;
return i;
}
int main() {
static int *ej[N], *ec[N], eo[N], *fi[N], *fc[N], fo[N];
int n, m, s, t, h, i, i_, j, j_, k, u, v, w, o1, o2, c1, c2;
long long d;
scanf("%d%d%d%d", &n, &m, &s, &t), s--, t--;
for (i = 0; i < n; i++) {
ej[i] = (int *) malloc(2 * sizeof *ej[i]);
ec[i] = (int *) malloc(2 * sizeof *ec[i]);
fi[i] = (int *) malloc(2 * sizeof *fi[i]);
fc[i] = (int *) malloc(2 * sizeof *fc[i]);
}
for (h = 0; h < m; h++) {
static char s[2];
int c, d;
scanf("%d%d%s", &i, &j, s), i--, j--;
switch (s[0]) {
case '(':
c = 0, d = 1;
break;
case ')':
c = 0, d = 2;
break;
case '[':
c = 1, d = 1;
break;
case ']':
c = 1, d = 2;
break;
case '{':
c = 2, d = 1;
break;
case '}':
c = 2, d = 2;
break;
case '<':
c = 3, d = 1;
break;
case '>':
c = 3, d = 2;
break;
default:
c = -1, d = 0;
break;
}
if (d == 1)
append(fi, fc, fo, j, i, c);
else
append(ej, ec, eo, i, j, c);
}
memset(dd, 0x3f, n * n * sizeof *dd);
for (i = 0; i < n; i++) {
u = i * n + i;
dd[u] = 0, pq_add_last(u);
}
while (cnt) {
u = pq_remove_first(), i = u / n, j = u % n;
if (i == s && j == t) {
printf("%lld\n", dd[u]);
return 0;
}
for (o1 = fo[i]; o1--; ) {
i_ = fi[i][o1], c1 = fc[i][o1];
for (o2 = eo[j]; o2--; ) {
j_ = ej[j][o2], c2 = ec[j][o2];
if (c1 == c2) {
w = i_ * n + j_, d = dd[u] + 2;
if (dd[w] > d) {
if (dd[w] == INF)
pq_add_last(w);
dd[w] = d, pq_up(w);
}
}
}
}
for (k = 0; k < n; k++) {
v = j * n + k, w = i * n + k, d = dd[u] + dd[v];
if (dd[w] > d) {
if (dd[w] == INF)
pq_add_last(w);
dd[w] = d, pq_up(w);
}
v = k * n + i, w = k * n + j, d = dd[v] + dd[u];
if (dd[w] > d) {
if (dd[w] == INF)
pq_add_last(w);
dd[w] = d, pq_up(w);
}
}
}
printf("-1\n");
return 0;
}
