Prize’s Fund of sponsor "I will give you more money than \textbf{2} preceding sponsors together" said new sponsor after \textbf{2} tournaments in which sponsor spent in S UAN for every tournament. The words like it said every next sponsor. You know a sum \textbf{S}, which give first sponsor, a number of regular tournament N and a sum of scoring in bank what have a sponsor, or that sum which he want to take in debt for prizes. \InputFile In the first line we have \textbf{3} numbers \textbf{S}, \textbf{N}, \textbf{B}. \textbf{S} ≤ \textbf{1000}, \textbf{0} < \textbf{N} ≤ \textbf{1000}, \textbf{B} ≤ \textbf{10^300}. \OutputFile One number is the sum which remains in scoring of sponsor or that sum which he want to take in debt.