Problem A - Diagonals
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Given that an n-gon has at least N diagonals, what is the minimum 
possible value of n?

Input 
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Input consists of multiple lines, one line per case. Each line contains 
a positive integer N ( N < 1015) that indicates the minimum possible 
number of diagonals. Input is terminated by a line containing a zero. 
This line should not be processed.

Output 
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For each line of input produce one line of output containing the minimum 
possible value for n (Number of sides).

Sample Input 
------------

10
100
1000
0

Output for Sample Input
-----------------------

7
16
47