RT。

#include <bits/stdc++.h>
using namespace std;
string s[500001];
int main() {
	int n, a = 0, b = 0, c = 0, d = 0;//首字母是M,C,O,I的个数
	scanf ("%d", &n);
	for (int i = 1; i <= n; ++i) {
		cin >> s[i];
		if (s[i][0] == 'M') ++a;
		if (s[i][0] == 'C') ++b;
		if (s[i][0] == 'O') ++c;
		if (s[i][0] == 'I') ++d;
	}
	unsigned long long k = 0;
    //四种组合排列方法
	k += a * b * c;
	k += a * b * d;
	k += a * c * d;
	k += b * c * d;
	printf ("%llu\n", k);
}