Two prisoners Jack and Jill are locked in a cell.
There is open window approx 40 feet above the ground of the cell.
They are never able to reach there.
Then they plan to escape by a tunnel and they start digging out.
After digging for more than 20 days, Jill comes with the different plan and they escaped.
What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?