$3$-phosphoglyceric acid $(3PGA)$ is the first stable product of Calvin-Bensen cycle or $C_{3}$ cycle.
Oxaloacetic acid (OAA) is first stable product of Hatch-Slack cycle or $C_{4}$-cycle.
Malic acid is produced in bundle sheath cells from $OAA$ in $C_{4}$ cycle. Phosphoenol pyruvic acid (PEP) is the first $C O_{2}$ acceptor in $C_{4}$-cycle.