I recently stumbled upon a problem which seems very easy, but I can't seem to find the solution.

If we have five positive numbers: { X1, X2, X3, X4, X5 }, we can form ten distinct pairs of these five numbers. Given the sum of each pair, you are asked to find the original five numbers.
All numbers are positive integers bellow 1,000,000,000.

Any hints or solutions would be appreciated. :D