This is Part 9 of the “Let’s play EVM Puzzles” series, where I will explain how to solve each puzzle challenge.

EVM Puzzlesis a project developed by Franco Victorio (@fvictorio_nan) that is a perfect fit if you are in the process of learning how the Ethereum EVM works, and you want to apply some of the knowledge you have just acquired.

# EVM Puzzle 9

`00 36 CALLDATASIZE`

01 6003 PUSH1 03

03 10 LT

04 6009 PUSH1 09

06 57 JUMPI

07 FD REVERT

08 FD REVERT

09 5B JUMPDEST

0A 34 CALLVALUE

0B 36 CALLDATASIZE

0C 02 MUL

0D 6008 PUSH1 08

0F 14 EQ

10 6014 PUSH1 14

12 57 JUMPI

13 FD REVERT

14 5B JUMPDEST

15 00 STOP

This puzzle is much simpler compared to the previous one. It’s just a question to solve some math equations.

Let’s see what new opcodes have been introduced:

- LT: pop 2 values from the stack and push the result of
`value0 < value1`

to the stack. If the result is true, it pushes`1`

otherwise`0`

. - CALLVALUE: push to the stack the value of the current call in
`wei`

## Block 1: check calldata size

`00 36 CALLDATASIZE`

01 6003 PUSH1 03

03 10 LT

04 6009 PUSH1 09

06 57 JUMPI

07 FD REVERT

08 FD REVERT

09 5B JUMPDEST

This block check if the size in byte of the `calldata`

is less than 3. If so, it does not follow the `JUMPI`

jump and revert. That’s our first requirement. Our `calldatasize`

must be greater or equal of 3.

## Block 2: Check the calldata size and value

`09 5B JUMPDEST`

0A 34 CALLVALUE

0B 36 CALLDATASIZE

0C 02 MUL

0D 6008 PUSH1 08

0F 14 EQ

10 6014 PUSH1 14

12 57 JUMPI

13 FD REVERT

14 5B JUMPDEST

15 00 STOP

The next block of code instead push to the stack the multiplication of `calldata` size in bytes and calldata value in `wei`.

If the result is not equal to `8`

it will not follow the `JUMPI`

jump and revert. This means that the second requirement is that `MUL(calldata_size, calldata_value)`

must be equal to `8`

.

## Solution

There are many possible solutions, we just need to follow these requirements:

`CALLDATASIZE >= 3`

`CALLVALUE * CALLDATASIZE === 8`

For example, `0xFFFFFFFFFFFFFFFF`

as calldata and `1 wei`

as value will solve the challenge, but also `0xFFFFFFFF`

and `2 wei`

will do it!

Here’s the link to the solution of Puzzle 9 on EVM Codes website to simulate it.