#include <bits/stdc++.h>
using namespace std;

int n, cnt;
char a, b;
bool vis [130][130];

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {

		cin >> a >> b;
		if (!vis[a][b]) {
			cnt ++;
			vis[a][b] = 1;
		}

	}

	cout << 52 - cnt;
}