#include using namespace std; int main() { int n; cin >> n; for (int i = 6; i < n; i += 6) { int firstToCheck = i - 1; int secondToCheck = i + 1; //prime check bool isFirstPrime = true; double temp = sqrt(firstToCheck); for (int j = 2; j <= temp; j++) { if (firstToCheck % j == 0) isFirstPrime = false; } if (!isFirstPrime) continue; //prime check bool isSecondPrime = true; double temp2 = sqrt(secondToCheck); for (int j = 2; j <= temp2; j++) { if (secondToCheck % j == 0) isSecondPrime = false; } if (isSecondPrime) cout << firstToCheck << " " << secondToCheck << endl; } }