void main() {
    for (int number = 1; number <= 20; number++) {
        if (number % 3 != 0) {
            continue;
        }
        IO.println(number);
    }
}

// From Groundwork, chapter 5 (ch05-repetition), box 14.
// This example is from Groundwork, licensed CC BY-NC-SA 4.0.
// Run with: java ch05_14.java