# FCSC - Fibonacci

Published on Sep 1, 2023 by Cartoone.

for this series of challenge we are asked to write code in assembler for the first challenge my algorithm was very simple (at the same time given the problem ^^)

note that I use work register 6 as the reference value for the —

```
R5 --
R1 = 0
R2 = 1
R4 = 0
do
{
R3 = R2 + R1
R1 = R2
R2 = R3
R5 --
} while (R5 != 0)
R0 = R3
exit
```

```
MOV R6,#1
SUB R5,R5,R6
MOV R1,#0
MOV R2,#1
MOV R6,#1
MOV R4,#0
JR A
A:
ADD R3, R2, R1
MOV R1,R2
MOV R2,R3
SUB R5,R5,R6
CMP R5,R4
JZR B
JR A
B:
MOV R0,R3
STP
```

which gives us the machine code :

`800600014dad80010000800200018006000180040000CF004a53002100324dad0645C701CFF900301400`

which gives us the flag :

`FCSC{770ac04f9f113284eeee2da655eba34af09a12dba789c19020f5fd4eff1b1907}`