Problem:
Score : 300 points

Problem Statement

There are N people. The name of the i-th person is S_i.

We would like to choose three people so that the following conditions are met:

The name of every chosen person begins with M, A, R, C or H.

There are no multiple people whose names begin with the same letter.

How many such ways are there to choose three people, disregarding order?

Note that the answer may not fit into a 32-bit integer type.

Constraints

1 \leq N \leq 10^5

S_i consists of uppercase English letters.

1 \leq |S_i| \leq 10

S_i \neq S_j (i \neq j)

Input

Input is given from Standard Input in the following format:

N
S_1
:
S_N

Output

If there are x ways to choose three people so that the given conditions are met, print x.

Sample Input 1

5
MASHIKE
RUMOI
OBIRA
HABORO
HOROKANAI

Sample Output 1

2

We can choose three people with the following names:

MASHIKE, RUMOI, HABORO

MASHIKE, RUMOI, HOROKANAI

Thus, we have two ways.

Sample Input 2

4
ZZ
ZZZ
Z
ZZZZZZZZZZ

Sample Output 2

0

Note that there may be no ways to choose three people so that the given conditions are met.

Sample Input 3

5
CHOKUDAI
RNG
MAKOTO
AOKI
RINGO

Sample Output 3

7

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Text;
using static System.Convert;
using static System.Math;
using static Extensions;
using static MathExtensions;

public static class Program
{
    public static void Solve()
    {
        var n = I;
        var s = Ss(n);

        var b = new long[]
        {
            s.Count(x => x[0] == 'M'),
            s.Count(x => x[0] == 'A'),
            s.Count(x => x[0] == 'R'),
            s.Count(x => x[0] == 'C'),
            s.Count(x => x[0] == 'H'),
        };

        var ans = 0L;

        foreach (var i in Range(3))
            foreach(var j in Range(i + 1, 4))
                foreach(var k in Range(j + 1, 5))
                    ans += b[i] * b[j] * b[k];

        Console.WriteLine(ans);
    }

    #region Scanners
    static TextScanner _ts;

    static char C => char.Parse(_ts.Next());
    static string S => _ts.Next();
    static int I => int.Parse(_ts.Next());
    static long L => long.Parse(_ts.Next());
    static BigInteger B => BigInteger.Parse(_ts.Next());
    static double D => double.Parse(_ts.Next());

    static char[] Cs(int count) => Repeat(count, () => C).ToArray();
    static string[] Ss(int count) => Repeat(count, () => S).ToArray();
    static int[] Is(int count) => Repeat(count, () => I).ToArray();
    static long[] Ls(int count) => Repeat(count, () => L).ToArray();
    static BigInteger[] Bs(int count) => Repeat(count, () => B).ToArray();
    static double[] Ds(int count) => Repeat(count, () => D).ToArray();
    #endregion

    public static void Main()
    {
        var sw = new StreamWriter(Console.OpenStandardOutput());
        sw.NewLine = "\n";
#if DEBUG
        sw.AutoFlush = true;
#else
        sw.AutoFlush = false;
#endif
        Console.SetOut(sw);
        _ts = new TextScanner(Console.In);
        Solve();
        Console.Out.Flush();
    }
}

public static partial class Extensions
{
    public static T[] Sort<T>(this T[] array)
        where T : IComparable<T>
    {
        Array.Sort(array);
        return array;
    }

    public static T[] SortDescending<T>(this T[] array)
        where T : IComparable<T>
    {
        Array.Sort(array, Comparer<T>.Create((x, y) => y.CompareTo(x)));
        return array;
    }

    public static T[] SortBy<T, TKey>(this T[] array, Func<T, TKey> keySelector)
        where TKey : IComparable<TKey>
    {
        Array.Sort(array, Comparer<T>.Create((x, y) => keySelector(x).CompareTo(keySelector(y))));
        return array;
    }

    public static T[] SortByDescending<T, TKey>(this T[] array, Func<T, TKey> keySelector)
        where TKey : IComparable<TKey>
    {
        Array.Sort(array, Comparer<T>.Create((x, y) => keySelector(y).CompareTo(keySelector(x))));
        return array;
    }
}

#pragma warning disable

public struct Point2D : IEquatable<Point2D>
{
    public Point2D(int y, int x)
    {
        this.Y = y;
        this.X = x;
    }

    public int Y { get; }

    public int X { get; }

    public static readonly Point2D Origin
        = new Point2D(0, 0);

    public static readonly IReadOnlyCollection<Point2D> NeumannNeighborhoodUnits
        = new[] { new Point2D(0, 1), new Point2D(1, 0), new Point2D(0, -1), new Point2D(-1, 0) };

    public static readonly IReadOnlyCollection<Point2D> MooreNeighborhoodUnits
        = new[]
        {
                new Point2D(-1, -1), new Point2D(-1, 0), new Point2D(-1, 1),
                new Point2D(0, -1), new Point2D(0, 1),
                new Point2D(1, -1), new Point2D(1, 0), new Point2D(1, 1),
        };

    public static IEnumerable<Point2D> EnumerateInnerPoints(Point2D max)
        => EnumerateInnerPoints(Origin, max);

    public static IEnumerable<Point2D> EnumerateInnerPoints(Point2D min, Point2D max)
    {
        if (min.X > max.X || min.Y > max.Y) throw new ArgumentException();
        for (var i = min.Y; i < max.Y; i++)
            for (var j = min.X; j < max.X; j++)
                yield return new Point2D(i, j);
    }

    public static int ManhattanDistance(Point2D source, Point2D target)
        => System.Math.Abs(source.X - target.X) + System.Math.Abs(source.Y - target.Y);

    public static int ChebyshevDistance(Point2D source, Point2D target)
        => System.Math.Max(System.Math.Abs(source.X - target.X), System.Math.Abs(source.Y - target.Y));

    public static Point2D operator +(Point2D left, Point2D right)
        => new Point2D(left.Y + right.Y, left.X + right.X);

    public static Point2D operator -(Point2D left, Point2D right)
        => new Point2D(left.Y - right.Y, left.X - right.X);

    public static bool operator ==(Point2D left, Point2D right)
        => left.Equals(right);

    public static bool operator !=(Point2D left, Point2D right)
        => !left.Equals(right);

    public bool IsIn(Point2D max)
        => this.IsIn(Origin, max);

    public bool IsIn(Point2D min, Point2D max)
    {
        if (min.X > max.X || min.Y > max.Y) throw new ArgumentException();
        return min.Y <= this.Y && this.Y < max.Y && min.X <= this.X && this.X < max.X;
    }

    public bool Equals(Point2D other)
        => this.Y == other.Y && this.X == other.X;

    public override bool Equals(object obj)
        => obj is Point2D ? this.Equals((Point2D)obj) : false;

    public override int GetHashCode()
        => (this.Y << 16) ^ this.X;

    public override string ToString()
        => $"{this.X} {this.Y}";
}

public partial class Grid2D<T>
{
    private T[] _grid;

    public Grid2D(int height, int width) : this(new Point2D(height, width)) { }

    public Grid2D(Point2D size)
    {
        _grid = new T[size.Y * size.X];
        this.Height = size.Y;
        this.Width = size.X;
        this.Size = size;
    }

    public Grid2D(T[][] grid)
    {
        this.Height = grid.Length;
        this.Width = grid.Max(r => r.Length);
        this.Size = new Point2D(this.Height, this.Width);
        _grid = new T[this.Height * this.Width];
        for (var i = 0; i < grid.Length; i++)
            for (var j = 0; j < grid[i].Length; j++)
                _grid[i * this.Width + j] = grid[i][j];
    }

    public int Height { get; }

    public int Width { get; }

    public Point2D Size { get; }

    public T this[int i, int j]
    {
        get { return _grid[i * this.Width + j]; }
        set { _grid[i * this.Width + j] = value; }
    }

    public T this[Point2D point]
    {
        get { return this[point.Y, point.X]; }
        set { this[point.Y, point.X] = value; }
    }
}

public class TextScanner
{
    private readonly TextReader _tr;

    public TextScanner(TextReader tr)
    {
        _tr = tr;
    }

    public string Next()
    {
        var sb = new StringBuilder();
        int i;
        do
        {
            i = _tr.Read();
            if (i == -1) throw new EndOfStreamException();
        }
        while (char.IsWhiteSpace((char)i));
        while (i != -1 && !char.IsWhiteSpace((char)i))
        {
            sb.Append((char)i);
            i = _tr.Read();
        }
        return sb.ToString();
    }
}

public static partial class Extensions
{
    public static void Answer(object value)
    {
        Console.WriteLine(value);
        Exit(0);
    }

    public static void Assert(bool condition)
    {
        if (!condition) throw new Exception("Assertion failed");
    }

    public static string AsString(this IEnumerable<char> source) => new string(source.ToArray());

    public static Dictionary<T, int> Bucket<T>(this IEnumerable<T> source) where T : IEquatable<T>
    {
        var dict = new Dictionary<T, int>();
        foreach (var item in source) if (dict.ContainsKey(item)) dict[item]++; else dict[item] = 1;
        return dict;
    }

    public static int[] Bucket<T>(this IEnumerable<T> source, int maxValue, Func<T, int> selector)
    {
        var arr = new int[maxValue + 1];
        foreach (var item in source) arr[selector(item)]++;
        return arr;
    }

    public static IComparer<T> CreateDescendingComparer<T>()
        where T : IComparable<T>
        => Comparer<T>.Create((x, y) => y.CompareTo(x));

    public static IEnumerable<int> CumSum(this IEnumerable<int> source)
    {
        var sum = 0;
        foreach (var item in source) yield return sum += item;
    }

    public static IEnumerable<long> CumSum(this IEnumerable<long> source)
    {
        var sum = 0L;
        foreach (var item in source) yield return sum += item;
    }

    public static void Exit(int exitCode)
    {
        Console.Out.Flush();
        Environment.Exit(exitCode);
    }

    public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
    {
        foreach (var item in source) action(item);
    }

    public static void ForEach<T, _>(this IEnumerable<T> source, Func<T, _> func)
    {
        foreach (var item in source) func(item);
    }

    public static void ForEach<T>(this IEnumerable<T> source, Action<T, int> action)
    {
        var i = 0;
        foreach (var item in source) action(item, i++);
    }

    public static void ForEach<T, _>(this IEnumerable<T> source, Func<T, int, _> func)
    {
        var i = 0;
        foreach (var item in source) func(item, i++);
    }

    // [l, r)
    public static bool IsIn<T>(this T value, T l, T r)
        where T : IComparable<T>
    {
        if (l.CompareTo(r) > 0) throw new ArgumentException();
        return l.CompareTo(value) <= 0 && value.CompareTo(r) < 0;
    }

    public static IEnumerable<int> Range(int start, int end, int step = 1)
    {
        for (var i = start; i < end; i += step) yield return i;
    }

    public static IEnumerable<int> Range(int end) => Range(0, end);

    public static void Repeat(int count, Action action)
    {
        for (var i = 0; i < count; i++) action();
    }

    public static void Repeat(int count, Action<int> action)
    {
        for (var i = 0; i < count; i++) action(i);
    }

    public static IEnumerable<T> Repeat<T>(int count, Func<T> func)
    {
        for (var i = 0; i < count; i++) yield return func();
    }

    public static IEnumerable<T> Repeat<T>(int count, Func<int, T> func)
    {
        for (var i = 0; i < count; i++) yield return func(i);
    }

    public static IEnumerable<int> RangeReverse(int start, int end, int step = 1)
    {
        for (var i = end - 1; i >= start; i -= step) yield return i;
    }

    public static IEnumerable<int> RangeReverse(int end) => RangeReverse(0, end);

    public static void Swap<T>(ref T x, ref T y)
    {
        var tmp = x; x = y; y = tmp;
    }
}

public static class MathExtensions
{
    public static int DivCeil(int left, int right)
        => left / right + (left % right == 0 ? 0 : 1);

    public static long DivCeil(long left, long right)
        => left / right + (left % right == 0L ? 0L : 1L);

    public static int Gcd(int left, int right)
    {
        int r;
        while ((r = left % right) != 0) { left = right; right = r; }
        return right;
    }

    public static long Gcd(long left, long right)
    {
        long r;
        while ((r = left % right) != 0L) { left = right; right = r; }
        return right;
    }

    public static BigInteger Gcd(BigInteger left, BigInteger right)
        => BigInteger.GreatestCommonDivisor(left, right);

    public static int HighestOneBit(int x)
    {
        x |= x >> 01;
        x |= x >> 02;
        x |= x >> 04;
        x |= x >> 08;
        x |= x >> 16;
        return x - (x >> 1);
    }

    public static long HighestOneBit(long x)
    {
        x |= x >> 01;
        x |= x >> 02;
        x |= x >> 04;
        x |= x >> 08;
        x |= x >> 16;
        x |= x >> 32;
        return x - (x >> 1);
    }

    public static int Lcm(int left, int right) => left / Gcd(left, right) * right;

    public static long Lcm(long left, long right) => left / Gcd(left, right) * right;

    public static BigInteger Lcm(BigInteger left, BigInteger right)
        => left / Gcd(left, right) * right;

    public static int Pow(int value, int exponent)
    {
        var r = 1;
        while (exponent > 0)
        {
            if ((exponent & 1) == 1) r *= value;
            value *= value;
            exponent >>= 1;
        }
        return r;
    }

    public static long Pow(long value, int exponent)
    {
        var r = 1L;
        while (exponent > 0)
        {
            if ((exponent & 1) == 1) r *= value;
            value *= value;
            exponent >>= 1;
        }
        return r;
    }

    public static long Fact(int value)
    {
        var r = 1L;
        for (var i = 2; i <= value; i++) r *= i;
        return r;
    }
}