What is printed as a result of executing the following code segment?

public class Main {
    public static void main(String[] args) {
        int[][] matrix = { {1, 2}, {3, 4}, {5, 6} };
        for (int i = 0; i < matrix.length; i++) {
            System.out.print(matrix[i][0] + " ");
        }
    }
}