The amino acid sequence of a peptide is $Phe-Leu-lle-Met-Ser-Leu$. The number of codons that encode the amino acids present in this peptide is given below:
Phe: $2$ codons
Leu: $6$ codons
Ile: $3$ codons
Met: $1$ codon
Ser: $4$ codons
The number of unique $DNA$ sequences that can encode this peptide is ___________.