Equipment Serial Number; uniquely identifies equipment and is embedded electronically by the manufacturer. The ESN is in two forms the DEC (decimal) and HEX (hexadecimal) form.

NOTE: Don't confuse the letter O with the number 0 (zero). It is always a zero. Only letters A-F are in an ESN/MEID

Your task is change ESN to A31337133713373. you can verify your flag at http://ctf.hpandro.raviramesh.info