#include <iostream>
#include <string>

using namespace std;

constexpr int MAX_NODES = 10 * 1000 * 1000;

int refs[MAX_NODES][26] = {};
int num_strings[MAX_NODES] = {};

int sum_lengths(int node, int len) {
	if (num_strings[node] == 1) {
		return len;
	}

	int res = 0;
	for (int l = 0; l < 26; l++) {
		if (refs[node][l]) {
			res += sum_lengths(refs[node][l], len + 1);
		}
	}
	return res;
}

int main() {
	int cur_nodes = 1, n, l;
	cin >> n >> l;
	for (int i=0; i < n; i++) {
		string S;
		cin >> S;
		int loc = 0;
		num_strings[loc]++;
		for (char ch : S) {
			if (refs[loc][ch - 'a'] == 0) {
				refs[loc][ch - 'a'] = cur_nodes++;
			}
			loc = refs[loc][ch - 'a'];
			num_strings[loc]++;
		}
	}

	cout << sum_lengths(0, 0) << endl;
	cerr << cur_nodes << endl;
	return 0;
}