1152 Google Recruitment （20 分）

//1152 Google Recruitment :Find prime
#include 
#include
#include
#include
using namespace std;

bool find(string a) {
	int b = stoi(a);
	int i;
	//if (b == 3) return true;
	if (b == 2) return true;
	if (b == 1)return false;
	for (i = 2; i*i <= b; i++) {
		if (b%i == 0)
			return false;
	}
	return true;
}

int main() {
	int L, K;
	cin >> L >> K;
	string s;
	cin >> s;
	bool isfind = false;
	for (int i = 0; i + K <= s.length(); i++) {
		string a(s, i, K);
		if (find(a)) {
			cout << a;
			isfind = true;
			break;
		}
	}
	if (isfind == false)
		cout << "404";
	return 0;
}