Language: C++

/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>
#include <random>

// container library
#include <array>
#include <bitset>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T>
using PQ = priority_queue<T>;
template <typename T>
using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define gsort(b, e) sort(b, e, greater<decltype(*b)>())

/* ----------- debug ---------- */

template <class T>
ostream& operator<<(ostream& os, vector<T> v) {
	os << "[";
	for (auto vv : v)
		os << vv << ",";
	return os << "]";
}

template <class T>
ostream& operator<<(ostream& os, set<T> v) {
	os << "[";
	for (auto vv : v)
		os << vv << ",";
	return os << "]";
}

template <class L, class R>
ostream& operator<<(ostream& os, pair<L, R> p) {
	return os << "(" << p.fst << "," << p.snd << ")";
}

/* ---------- Constants ---------- */

// const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// mt19937 mert(LL(time(0)));

/* ---------- Short Functions ---------- */

template <typename T>
T sq(T a) {
	return a * a;
}

template <typename T>
T gcd(T a, T b) {
	if (a > b) return gcd(b, a);
	return a == 0 ? b : gcd(b % a, a);
}

template <typename T, typename U>
T mypow(T b, U n) {
	if (n == 0) return 1;
	if (n == 1) return b /* % MOD */;
	if (n % 2 == 0) {
		return mypow(b * b /* % MOD */, n / 2);
	}
	else {
		return mypow(b, n - 1) * b /* % MOD */;
	}
}

ll pcnt(ll b) {
	return __builtin_popcountll(b);
}



// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};
// const ll dx[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
// const ll dy[8] = {-1, -1, -1, 0, 0, 1, 1, 1};

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N;
	cin >> N;
	int cnt_M = 0, cnt_A = 0, cnt_R = 0, cnt_C = 0, cnt_H = 0;
	REP(i, N) {
		char S;
		cin >> S;
		if (S[0] == 'M') cnt_M++;
		else if (S[0] == 'A')  cnt_A++;
		else if (S[0] == 'R')  cnt_R++;
		else if (S[0] == 'C')  cnt_C++;
		else if (S[0] == 'H')  cnt_H++;
	}
	cout << cnt_M * cnt_A*cnt_R*cnt_C*cnt_H << endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:138:13: error: 'i' was not declared in this scope
  138 |         REP(i, N) {
      |             ^
a.cc:138:9: error: 'REP' was not declared in this scope
  138 |         REP(i, N) {
      |         ^~~