Simple one, solved using zbarimg and stegosolve
We are given a qrcode result.png which when passed to zbarimg produces an equation.
```kakdroog@kali:~/Documents/liveCTF/volgactf19/crypto/joi$ zbarimg result.png QR-Code:C_F(n1, n2) = 14 * [C(n1,n2) / 14] + 7 * FLAG(n1,n2) + (C(n1,n2) mod 7)scanned 1 barcode symbols from 1 images in 0.06 seconds```
Guessed this to be a rabbit hole, thank fuck ;)
Fired up stegosolve and found working qrcode in RED Plane, saved as bmp and converted to png
```kakdroog@kali:~/Documents/liveCTF/volgactf19/crypto/joi$ zbarimg solved.png QR-Code:VolgaCTF{5t3g0_m4tr3shk4_in_4cti0n}scanned 1 barcode symbols from 1 images in 0.06 seconds```
YAY Flag!
> VolgaCTF{5t3g0_m4tr3shk4_in_4cti0n}