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Problems

The presents to the 8th of March

The presents to the 8th of March

Boys decided to prepare presents for girls on a holiday of 8th of March. When they were preparing presents, they quickly put there a congratulation postcard and a soft toy. But when they began to put mandarins, they came face to face with such trouble. At first they wanted to put m mandarins in every package (and in other packages - apples), but they couldn't do it because in one package were m - 1 mandarins. Then they decided to put m - 1 mandarins, but m - 2 mandarins left. Then they decided to put m - 2 mandarins, but m - 3 mandarins left, and so on. When they decide to put 2 mandarins, then 1 mandarin left. How many mandarins did the boys buy?

prb55

Input

The number of mandarins m (1 < m1000), that the boys wanted to put initially into the presents.

Output

The minimum possible number of mandarins, that the boys bought as a gift for the girls.

Time limit 1 second
Memory limit 128 MiB
Input example #1
4
Output example #1
11