103*. On seven cards, the numbers $1,2,3,4,5,6$ and 7 were written. Then the cards were flipped, shuffled, and the same numbers $1,2,3,4,5,6$, 7 were written on the reverse sides. The numbers written on both sides of each card were added, and the resulting sums were multiplied. Is the resulting product even or odd?
$\triangle$ Suppose the product is odd. For this to be true, all 7 factors must be odd. But then, for the four cards with odd numbers 1, 3, 5, and 7 on one side, the numbers on the other side must be even. However, there are only three even numbers here.

Therefore, this case is impossible.

Answer: even.