#include <iostream>
#include <vector>

using namespace std;

int main() {
	int n;
	cin >> n;

	vector<string> nums(n);
	for (int i = 0; i < n; i++) {
		cin >> nums[i];
	}

	int res = 0;
	vector<int> dp(n);
	dp[1] = dp[2] = 1;
	for (int i = 3; i < 10000; i++) {
		dp[i] = dp[i - 1] + i - 1;
	}

	int number = nums[0].size();
	int prev_len = INT_MAX;
	for (int i = 0; i < number; i++) {
		int hash[26] = {0}, len = 0;
		// 统计一下这里列最多的相同字母的数量
		for (int j = 0; j < n; j++) {
			hash[nums[j][i] - 'a']++;
			len = max(len, min(prev_len, hash[nums[j][i] - 'a'] ) );
		}

		prev_len = len;
		if (i == 0)
			res += dp[len + 1];
		else
			res += dp[len];
	}

	cout << res << endl;

	return 0;
}