#include <bits/stdc++.h>
/* Defines */
using u64 = uint64_t;
constexpr size_t MAX_CHARS = 6;
/* Function definitions */
void readInput();
u64 countPairs(const std::vector<size_t> &sourse, const size_t indexToCheck);
/* Global variables */
std::vector<std::array<char, MAX_CHARS + 1>> input;
/* Function declarations */
void readInput () {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
size_t wordCount, letterCount;
std::cin >> wordCount >> letterCount;
input.resize(wordCount);
for (auto &word: input)
std::cin >> word.data();
std::ios_base::sync_with_stdio(true);
std::cin.tie(&std::cout);
}
u64 countPairs (const std::vector<size_t> &source, const size_t indexToCheck) {
static constexpr std::array<char, 26> alphabet = {
'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
'w', 'x', 'y', 'z'
};
if (input[0][indexToCheck] == '\0') {
const u64 count = static_cast<u64>(source.size());
return count * (count - 1) / 2;
}
if (source.size() < 2)
return 0;
std::array<std::vector<size_t>, 'z' + 1> prefixes;
static_assert(prefixes.size() > '?', "Internal asumption error");
for (auto inputIndex: source) {
const char c = input[inputIndex][indexToCheck];
if ('a' <= c && c <= 'z')
prefixes[c].emplace_back(inputIndex);
else if (c == '?') {
prefixes['?'].emplace_back(inputIndex);
for (char i: alphabet)
prefixes[i].emplace_back(inputIndex);
} else
assert(false);
}
const u64 falsePairs = countPairs(prefixes['?'], indexToCheck + 1);
u64 result = 0;
for (const char c: alphabet)
if (prefixes[c].size() >= 1 + prefixes['?'].size()) {
result += countPairs(prefixes[c], indexToCheck + 1) - falsePairs;
}
return result + falsePairs;
}
int main () {
readInput();
std::vector<size_t> allIndexes(input.size());
std::iota(allIndexes.begin(), allIndexes.end(), 0);
std::cout << countPairs(allIndexes, 0) << '\n';
}
