#include <string>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;

const int INF = 1012345678;
const int D = 10;
const int A = 26;

int maximum_independent_set(int N, const vector<vector<bool> >& mat) {
	vector<int> g(N);
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < N; j++) {
			if (mat[i][j]) {
				g[i] |= 1 << j;
			}
		}
	}
	int ans = 0;
	auto dfs = [&](auto& self, int x, int bit) -> void {
		if (x == N) {
			ans = max(ans, __builtin_popcount(bit));
			return;
		}
		self(self, x + 1, bit);
		if ((g[x] & bit) == 0) {
			self(self, x + 1, bit | (1 << x));
		}
	};
	dfs(dfs, 0, 0);
	return ans;
}

int main() {
	int N;
	cin >> N;
	vector<vector<int> > lists(1 << D);
	for (int i = 0; i < N; i++) {
		string S;
		cin >> S;
		int bit1 = 0, bit2 = 0;
		for (char c : S) {
			if ('0' <= c && c <= '9') {
				bit1 |= 1 << (c - '0');
			} else {
				bit2 |= 1 << (c - 'A');
			}
		}
		lists[bit1].push_back(bit2);
	}
	for (int i = 0; i < (1 << D); i++) {
		sort(lists[i].begin(), lists[i].end());
		lists[i].erase(unique(lists[i].begin(), lists[i].end()), lists[i].end());
	}
	int ans = INF;
	for (int i = 0; i < (1 << D); i++) {
		vector<int> contain;
		for (int j = 0; j < (1 << D); j++) {
			if ((i & j) == j) {
				contain.push_back(j);
			}
		}
		bool valid = true;
		vector<bool> used(A, false);
		vector<vector<bool> > mat(A, vector<bool>(A, false));
		vector<int> deg(A, 0);
		for (int j : contain) {
			for (int k : lists[j]) {
				if (k == 0) {
					valid = false;
				} else if (!(k & (k - 1))) {
					used[__builtin_ctz(k)] = true;
				} else {
					int a = __builtin_ctz(k);
					int b = __builtin_ctz(k - (1 << a));
					mat[a][b] = true;
					mat[b][a] = true;
					deg[a]++;
					deg[b]++;
				}
			}
		}
		if (valid) {
			vector<int> index(A, -1);
			int cnt = 0;
			int score = D - __builtin_popcount(i);
			for (int j = 0; j < A; j++) {
				if (used[j]) {
					score++;
				} else if (deg[j] >= 1) {
					index[j] = cnt++;
				}
			}
			vector<vector<bool> > nmat(cnt, vector<bool>(cnt, false));
			for (int j = 0; j < A; j++) {
				for (int k = 0; k < A; k++) {
					if (!used[j] && !used[k] && mat[j][k]) {
						nmat[index[j]][index[k]] = true;
					}
				}
			}
			int res = maximum_independent_set(cnt, nmat);
			score += cnt - res;
			ans = min(ans, score);
		}
	}
	cout << ans << endl;
	return 0;
}