Next one in the series P40593

Consider the series $$0,~ 0 + 1,~ 0 + 1 + 2,~ 0 + 1 + 2 + 3,~ 0 + 1 + 2 + 3 + 4,~ \dots \quad = \quad 0,~ 1,~ 3,~ 6,~ 10,~ \dots$$ Write a program that, for every given natural number $n$, prints the first number of the series greater than or equal to $n$.

Input

Input consists of a sequence of natural numbers $n$.

Output

For every $n$, print the first number of the series $0, 1, 3, 6, \dots$ that is greater than or equal to $n$.