In the song NDaysOfChristmas, the number of elements in the gifts increases in each iteration. Justify the total number of elements the recipient receives after N days. What is the total number based on the standard version, with N = 12?

NDAYSOFCHRISTMAS(gifts 2.. n): for i-1 to n Sing "On the ith day of Christmas, my true love gave to me" for j l down to 2 Sing "j gifts [j]" Sing "and" Sing "a partridge in a pear tree