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1153. Supercomputer

Time limit: 2.0 second
Memory limit: 64 MB
To check the speed of JCN Corporation new supercomputer it was decided to figure out the sum of first N (N < 10600) positive integers. Unfortunately, by the time the calculation was finished the Chief Programmer forgot the value of N he entered. Your task is to write the program (for personal computer), which would determine the value of N by the result calculated on supercomputer.
Note: JCN Corporation manufactures only reliable computers, and its programmers write only correctly working programs.

Input

One line containing the result of calculations on the supercomputer.

Output

Выведите N, the number entered by Chief Programmer.

Sample

inputoutput
28
7
Problem Author: Eugene Bryzgalov
Problem Source: Ural Collegiate Programming Contest, April 2001, Perm, English Round