using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; using System.IO; using static util; using P = pair; using Binary = System.Func; using Unary = System.Func; class Program { static StreamWriter sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; static Scan sc = new Scan(); const int M = 1000000007; const int M2 = 998244353; const long LM = (long)1e18; const double eps = 1e-11; static readonly int[] dd = { 0, 1, 0, -1, 0 }; const string dstring = "RDLU"; static void Main() { int n, m; sc.Multi(out n, out m); var s = sc.Str; var edge = new List[n]; var cnt = new long[n]; var q = new Queue(); for (int i = 0; i < n; i++) { edge[i]= new List(); if (s[i] == 'P') { ++cnt[i]; q.Enqueue(i); } } var dic = new int[128]; dic['P'] = 0; dic['D'] = 1; dic['C'] = 2; dic['A'] = 3; for (int i = 0; i < m; i++) { int a, b; sc.Multi(out a, out b); --a; --b; if (dic[s[a]] + 1 == dic[s[b]]) edge[a].Add(b); if (dic[s[b]] + 1 == dic[s[a]]) edge[b].Add(a); } while (q.Any()) { int p = q.Dequeue(); foreach (var item in edge[p]) { if (cnt[item] == 0) q.Enqueue(item); cnt[item] += cnt[p]; } } long ans = 0; for (int i = 0; i < n; i++) { if (s[i] == 'A') ans += cnt[i]; } Prt(ans); sw.Flush(); } static void DBG(string a) => Console.WriteLine(a); static void DBG(IEnumerable a) => DBG(string.Join(" ", a)); static void DBG(params object[] a) => DBG(string.Join(" ", a)); static void Prt(string a) => sw.WriteLine(a); static void Prt(IEnumerable a) => Prt(string.Join(" ", a)); static void Prt(params object[] a) => Prt(string.Join(" ", a)); } class pair : IComparable> { public T v1; public U v2; public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; } public int CompareTo(pair a) { int c = Comparer.Default.Compare(v1, a.v1); return c != 0 ? c : Comparer.Default.Compare(v2, a.v2); } public override string ToString() => v1 + " " + v2; public void Deconstruct(out T a, out U b) { a = v1; b = v2; } } static class util { public static pair make_pair(this IList l) => make_pair(l[0], l[1]); public static pair make_pair(T v1, U v2) => new pair(v1, v2); public static T sq(T a) => Operator.Multiply(a, a); public static T Max(params T[] a) => a.Max(); public static T Min(params T[] a) => a.Min(); public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w; public static void swap(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; } public static void swap(this IList a, int i, int j) where T : struct { var t = a[i]; a[i] = a[j]; a[j] = t; } public static T[] copy(this IList a) { var ret = new T[a.Count]; for (int i = 0; i < a.Count; i++) ret[i] = a[i]; return ret; } } static class Operator { static readonly ParameterExpression x = Expression.Parameter(typeof(T), "x"); static readonly ParameterExpression y = Expression.Parameter(typeof(T), "y"); public static readonly Func Add = Lambda(Expression.Add); public static readonly Func Subtract = Lambda(Expression.Subtract); public static readonly Func Multiply = Lambda(Expression.Multiply); public static readonly Func Divide = Lambda(Expression.Divide); public static readonly Func Plus = Lambda(Expression.UnaryPlus); public static readonly Func Negate = Lambda(Expression.Negate); public static Func Lambda(Binary op) => Expression.Lambda>(op(x, y), x, y).Compile(); public static Func Lambda(Unary op) => Expression.Lambda>(op(x), x).Compile(); } class Scan { public int Int => int.Parse(Str); public long Long => long.Parse(Str); public double Double => double.Parse(Str); public string Str => Console.ReadLine().Trim(); public pair Pair() where T : IComparable where U : IComparable { T a; U b; Multi(out a, out b); return new pair(a, b); } public int[] IntArr => StrArr.Select(int.Parse).ToArray(); public long[] LongArr => StrArr.Select(long.Parse).ToArray(); public double[] DoubleArr => StrArr.Select(double.Parse).ToArray(); public string[] StrArr => Str.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries); bool eq() => typeof(T).Equals(typeof(U)); T ct(U a) => (T)Convert.ChangeType(a, typeof(T)); T cv(string s) => eq() ? ct(int.Parse(s)) : eq() ? ct(long.Parse(s)) : eq() ? ct(double.Parse(s)) : eq() ? ct(s[0]) : ct(s); public void Multi(out T a) => a = cv(Str); public void Multi(out T a, out U b) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); } public void Multi(out T a, out U b, out V c) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); } public void Multi(out T a, out U b, out V c, out W d) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); } public void Multi(out T a, out U b, out V c, out W d, out X e) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); e = cv(ar[4]); } public void Multi(out T a, out U b, out V c, out W d, out X e, out Y f) { var ar = StrArr; a = cv(ar[0]); b = cv(ar[1]); c = cv(ar[2]); d = cv(ar[3]); e = cv(ar[4]); f = cv(ar[5]); } }