import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken.to!int; } long readLong() { return readToken.to!long; } real readReal() { return readToken.to!real; } bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } } bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } } int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; } int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); } int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); } int N; string S; int[] A, B; char[] C; int[][] G; int[] us; int[] pari; void dfs(int u, int pi) { us ~= u; pari[u] = pi; foreach (i; G[u]) if (pi != i) { if (B[i] == u) { swap(A[i], B[i]); } dfs(B[i], i); } } void main() { try { for (; ; ) { N = readInt; S = readToken; A = new int[N - 1]; B = new int[N - 1]; C = new char[N - 1]; foreach (i; 0 .. N - 1) { A[i] = readInt - 1; B[i] = readInt - 1; C[i] = readToken[0]; } G = new int[][N]; foreach (i; 0 .. N - 1) { G[A[i]] ~= i; G[B[i]] ~= i; } us = []; pari = new int[N]; dfs(0, -1); const SLen = cast(int)(S.length); auto up = new int[][](N - 1, SLen + 1); auto dn = new int[][](N - 1, SLen + 1); foreach_reverse (u; us) { const i = pari[u]; if (~i) { // start foreach (k; 0 .. SLen) { if (C[i] == S[k ]) chmax(up[i][k + 1], 1); if (C[i] == S[SLen - 1 - k]) chmax(dn[i][k + 1], 1); } // trans foreach (k; 0 .. SLen) { chmax(up[i][k + 1], up[i][k]); chmax(dn[i][k + 1], dn[i][k]); } const j = pari[A[i]]; if (~j) { foreach (k; 0 .. SLen + 1) { chmax(up[j][k], up[i][k]); chmax(dn[j][k], dn[i][k]); } foreach (k; 0 .. SLen) { if (C[j] == S[k ]) chmax(up[j][k + 1], up[i][k] + 1); if (C[j] == S[SLen - 1 - k]) chmax(dn[j][k + 1], dn[i][k] + 1); } } } } debug { writeln("A = ", A); writeln("B = ", B); writeln("up = ", up); writeln("dn = ", dn); } int ans; foreach (u; us) foreach (k; 0 .. SLen + 1) { int[2] mxs = [0, 0]; int[2] js = [-1, -1]; foreach (i; G[u]) if (A[i] == u) { int tmp = up[i][k]; int j = i; static foreach (h; 0 .. 2) { if (mxs[h] < tmp) { swap(mxs[h], tmp); swap(js[h], j); } } } foreach (i; G[u]) if (A[i] == u) { const mx = mxs[(js[0] != i) ? 0 : 1]; debug { writefln("u = %s, k = %s, i = %s: %s + %s", u, k, i, mx, dn[i][SLen - k]); } chmax(ans, mx + dn[i][SLen - k]); } } writeln(ans); } } catch (EOFException e) { } }