bool isPrime(int n) {
    if (n < 2) return false;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) return false;
    }
    return true;
}

vector<int> findCycle(int p) {
    vector<int> cycle;
    map<int, bool> seen;
    int current = p % 10;

    while (!seen[current]) {
        cycle.push_back(current);
        seen[current] = true;
        current = (current * p) % 10;
    }
    return cycle;
}

int primeAssignment(int M, int N) {
    vector<int> primes;
    for (int i = M; i <= N; i++) {
        if (isPrime(i)) primes.push_back(i);
    }

    map<int, int> lastDigitCount;
    for (int prime : primes) {
        vector<int> cycle = findCycle(prime);
        for (int digit : cycle) {
            lastDigitCount[digit]++;
        }
    }

    int maxCount = 0;
    for (auto &entry : lastDigitCount) {
        maxCount = max(maxCount, entry.second);
    }

    return maxCount;
}