题解

#include <iostream>
#include <vector>
using namespace std;
bool isPrime(int num) {
if (num <= 1) return false;
if (num == 2 || num == 3) return true;
if (num % 2 == 0 || num % 3 == 0) return false;
for (int i = 5; i * i <= num; i += 6) {
if (num % i == 0 || num % (i + 2) == 0) return false;
}
return true;
}

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

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

vector<int> indices(m);
for (int i = 0; i < m; ++i) {
    cin >> indices[i];
}

int sum = 0;
for (int i = 0; i < m; ++i) {
    if (isPrime(cards[indices[i] - 1])) {
        sum += cards[indices[i] - 1];
    }
}

cout << sum << endl;

return 0;

}