Cells in a circle

On a sheet of graph paper, a circle with radius R is drawn, centered at the intersection of the grid lines. Determine how many complete cells are contained within this circle.

Input

You are given a single non-negative integer R on one line, representing the radius of the circle. The constraints are 0 ≤ R ≤ 1000.

Output

Output a single integer, which is the number of complete cells contained within the circle.

Examples