Where is the cadenza in Shotstakovich's Cello Concerto No. 1

The first movement begins with its four-note main theme derived from the composer's DSCH motif, although the intervals, rhythm and shape of the motto are continually distorted and re-shaped throughout the movement. It's also related to a theme from the composer's score for the 1948 film: The Young Guard, which illustrates a group of Soviet soldiers being marched to their deaths at the hands of the Nazis. The theme reappears in Shostakovich's String Quartet No. 8 (1960).