A particle starts moving with constant acceleration. If its velocity after the time t is v, what will its displacement be in twice of that time?

Input

 First line contains two integers - the velocity of the particle v (0 ≤ v ≤100) and the time t (0 ≤ t ≤ 200), for which the particle gains that velocity.

Output

 Print a single integer in first line denoting the displacement in time 2t.

Samples