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Some particle starts moving from rest with constant acceleration. After time $t$ from the start of the motion, the particle's velocity became $v$. What distance will the particle travel in time $2t$?

Input

Each line is a separate test and contains two integers — the particle's velocity $v(0\le v\le 100)$ and the time $t(0\le t\le 200)$, at which the particle reached this velocity.

Output

For each test, print the distance the particle will move in time $2t$ on a separate line.

Examples