Earth is a constant subject to cosmic radiation from space. These cosmic rays are composed of charged particles, such as protons and nuclei of helium and heavier elements, but also high-energy photons ($$\gamma$$ radiation) and neutrinos. When these particles, travelling at a high speed of millions of kilometres per hour, collide with atoms and molecules in the earth's atmosphere nuclear reactions take place, which result in yet other particles and electromagnetic radiation, which has a shorter wavelength than $$\gamma$$ radiation. The earth's atmosphere consists for 80% of nitrogen. When neutrons from the cosmic rays collide with the atmosphere's nitrogen atoms, a part of the nitrogen is transformed to radioactive carbon-14 $${}^{14}\mathrm{C}$$. \[ {}^{1}\mathrm{n}+{}^{14}\mathrm{N} \to {}^{14}\mathrm{C}+{}^{1}\mathrm{H}\] Carbon-14 and ordinary carbon (carbon-12) are chemically equivalent. In the atmosphere they both react with oxygen, producing carbon dioxide. \[ \begin{aligned}{}^{14}\mathrm{C} + \mathrm{O}_2 &\to {}^{14}\mathrm{CO}_2 \\ {}^{12}\mathrm{C}+\mathrm{O}_2 &\to {}^{12}\mathrm{CO}_2\end{aligned}\]

As it turns out, the balance between $${}^{14}\mathrm{CO}_2$$ and $${}^{12}\mathrm{CO}_2$$ in the atmosphere has been as good as constant throughout time. This means that the amount of carbon-14, produced by cosmic radiation, must decay equally fast as a consequence of other factors. Plant tissue, which is made up of hydrocarbon compounds and contains both carbon-12 as carbon-14, absorbs carbon dioxide from the atmosphere during photosynthesis. As long as plants are alive, their tissue contains the same proportions of $${}^{14}\mathrm{C}$$ and $${}^{12}\mathrm{C}$$ as can be found in the atmosphere. When a plant dies, however, the photosynthesis stops, which eventually leads to a decrease in the amount of carbon-14.

The half-life of carbon-14 is approximately 5730 years. So if you find a dead plant (in the form of wood, burnt ashes, a cloth, corncobs, coal, peat or grain) which contains only half of the $${}^{14}\mathrm{C}$$ of a living plant this means the material is approx. 5730 years old. Living plants have a radioactive decay of approx. 15.3 carbon-14 atoms per minute for each gram of carbon they contain. The transformation of plant tissue to pure carbon would thus result in 15.3 counts per minute per gram of carbon on the Geiger counter, or in short 15.3 cpm/gC.

The facts above are the underlying basis of the $${}^{14}\mathrm{C}$$ dating method. This is a radiometric dating technique which makes use of the isotope carbon-14 in order to determine the age of dead organic material. The age $$t$$ (expressed in years) is given by the formula \[ t = -t_{\mathrm{half}}\times\log_2\frac{N}{N_0}\,.\] In this formula $$t_{\mathrm{half}}$$ represents the half-life of $${}^{14}\mathrm{C}$$, $$N_0$$ the number of $${}^{14}\mathrm{C}$$ atoms in the original (living) material and $$N$$ the number of $${}^{14}\mathrm{C}$$ atoms in the dead material. This dating method is suitable for materials up to about 60,000 years old. The method was developed in 1949 by Willard Frank Libby and his colleagues from the University of Chicago. In 1960, Libby was awarded the Nobel Prize in chemistry.

Input

One line with the value of $$N$$, the number of $${}^{14}\mathrm{C}$$ atoms in an examined sample, expressed in terms of cpm/gC.

Output

The age of the sample, based on the formula above, with $$t_{\mathrm{half}}=5730$$ years and $$N_0=15.3$$ cpm/gC. You don't have to do anything in particular if the age is estimated above 60,000 years.

Example

Input:

8.2

Output:

5156.05935217