1152. Google Recruitment (20).cpp

#include <iostream>
#include <string>
using namespace std;
bool isPrime(int n) {
    if (n == 0 || n == 1) return false;
    for (int i = 2; i * i <= n; i++)
        if (n % i == 0) return false;
    return true;
}
int main() {
    int l, k;
    string s;
    cin >> l >> k >> s;
    for (int i = 0; i <= l - k; i++) {
        string t = s.substr(i, k);
        int num = stoi(t);
        if (isPrime(num)) {
            cout << t;
            return 0;
        }
    }
    cout << "404\n";
    return 0;
}