euler 49

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

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

signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    for (int i = 1000; i <= 9999; i++) {
        if (prime(i)) {
            string s = to_string(i);
            sort(s.begin(), s.end());
            vector<int> v;
            do {
                if (s.starts_with('0')) continue;
                int n = stoi(s);
                if (prime(n)) {
                    for (int i = 0; i < v.size(); i++) {
                        for (int j = 0; j < i; j++) {
                            if (v[i] - v[j] == n - v[i]) {
                                cout << v[j] << v[i] << n << '\n';
                            }
                        }
                    }
                    v.push_back(n);
                }
            } while (next_permutation(s.begin(), s.end()));
        }
    }
}