SPOJ in Gyumri

   Aztec emperor Cuitl´ahuac is going to build a pyramid in his honor. This pyramid should be taller than previous ones.

   The Aztec pyramid is build out of stone blocks. Each block is 1×1×1-hunab cube. Cuitl´ahuac places first block on the ground during the foundation ceremony. Each of the following blocks must share a face with at least one of the previous blocks.

   The block is stable if it stands on the ground, or it stands on another block, that has a block or the ground next to each face. To stand the test of time the pyramid must be stable i.e. each block of it must be stable.

   Cuitl´ahuac asks you to determine the height of the tallest stable pyramid that can be built out of available blocks.

Input

   The only line of the input file contains a single integer numbern— the number of available blocks, including the first one (1 ≤n≤10⁹ ).

Output

   Output the height of the tallest stable pyramid that may be built out ofnblocks. The height must be output in hunabs.

Examples