BAC 4/19*/2022 4

#include <iostream>
using namespace std;

bool isPNr(int x) {
    int sum = 1 + x;
    for (int d = 2; d <= x / 2; d++) {
        if (x % d == 0) {
            sum += d;
        }
    }
    return sum % 2 == x % 2;
}

int kpn(int a, int b, int k) {
    int x;
    for (x = a; x <= b; x++) {
        if (isPNr(x)) {
            k--;
            if (!k) {
                return x;
            }
        }
    }
    return -1;
}

int main() {
    cout << kpn(27, 50, 3) << endl;
    return 0;
}