EN
Let X be a submartingale starting from 0, and Y be a semimartingale which is orthogonal and strongly differentially subordinate to X. The paper contains the proof of the sharp estimate
$ℙ(sup_{t≥0} |Y_t| ≥ 1) ≤ 3.375... ∥X∥₁$.
As an application, a related weak-type inequality for smooth functions on Euclidean domains is established.