Opening the PNG file we see at the top left of the letter I a group of pixels in black an white. Understanding them as “black=1” and “white=0” we obtain:

00110001001
10010001100
11001101000
01101010011
01100011011
10011100000

Concatenating them and deleting the last 2 zeros, we obtain “0011000100110010001100110011010000110101001101100011011100111000” what converted to ASCII becomes “12345678”, so the flag is: INSA{1234578}

By: fikih888