#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout << 18003 << "\n"; cout << 1 << " " << 2 << "\n"; cout << 1 << " " << 3 << "\n"; cout << 2 << " " << 4 << "\n"; cout << 2 << " " << 5 << "\n"; cout << 2 << " " << 6 << "\n"; cout << 3 << " " << 7 << "\n"; cout << 3 << " " << 8 << "\n"; cout << 3 << " " << 9 << "\n"; for(int i = 10; i <= 18003; i++) { cout << i-6 << " " << i << "\n"; } }