Update EIP-663: Fix markdown rendering

Merged by EIP-Bot.

Author: pdobacz

EIPS/eip-663.md

@@ -31,29 +31,26 @@ Introducing `SWAPN`, `DUPN` and `EXCHANGE` will provide an option to compilers t
 
 We introduce two new instructions:
 
- 1. `DUPN` (`0xe6`)
- 1. `SWAPN` (`0xe7`)
- 2. `EXCHANGE` (`0xe8`)
+1. `DUPN` (`0xe6`)
+2. `SWAPN` (`0xe7`)
+3. `EXCHANGE` (`0xe8`)
 
 If the code is legacy bytecode, any of these instructions result in an *exceptional halt*. (*Note: This means no change to behaviour.*)
 
 If the code is valid EOF1, the following rules apply:
 
- 1. The instructions are followed by an 8-bit immediate value, which we call `imm`, and can have a value of 0 to 255.
-  1.1 In the case of `DUPN` and `SWAPN`, we introduce the variable `n` which equals to `imm + 1`.
-  1.2 In the case of `EXCHANGE`, we introduce the variable `n` which is equal to `imm >> 4 + 1`, and the variable `m` which is equal to `imm & 0x0F + 1` (i.e., the first and second nibbles of `imm`, converted to one-indexing).
-
- 2. Code validation is extended to check that no relative jump instruction (`RJUMP`/`RJUMPI`/`RJUMPV`) targets immediate values of `DUPN`, `SWAPN` or `EXCHANGE`.
-
- 3. The stack validation algorithm of [EIP-5450](./eip-5450.md) is extended:
-  3.1. Before `DUPN` if the current stack height is less than `n`, code is invalid. After `DUPN`, the stack height is incremented.
-  3.2. Before `SWAPN` if the current stack height is less than `n + 1`, code is invalid. After `SWAPN`, the stack height is unchanged.
-  3.2. Before `EXCHANGE` if the current stack height is less than `n + m + 1`, code is invalid. After `EXCHANGE`, the stack height is unchanged.
-
- 4. Execution rules:
-  4.1. `DUPN`: the `n`'th stack item is duplicated at the top of the stack. (*Note: We use 1-based indexing here.*)
-  4.2. `SWAPN`: the `n + 1`'th stack item is swapped with the top of the stack.
-  4.3  `EXCHANGE`: the `n + 1`'th stack item is swapped with the `n + m + 1`'th stack item.
+1. The instructions are followed by an 8-bit immediate value, which we call `imm`, and can have a value of 0 to 255.
+   1. In the case of `DUPN` and `SWAPN`, we introduce the variable `n` which equals to `imm + 1`.
+   2. In the case of `EXCHANGE`, we introduce the variable `n` which is equal to `imm >> 4 + 1`, and the variable `m` which is equal to `imm & 0x0F + 1` (i.e., the first and second nibbles of `imm`, converted to one-indexing).
+2. Code validation is extended to check that no relative jump instruction (`RJUMP`/`RJUMPI`/`RJUMPV`) targets immediate values of `DUPN`, `SWAPN` or `EXCHANGE`.
+3. The stack validation algorithm of [EIP-5450](./eip-5450.md) is extended:
+   1. Before `DUPN` if the current stack height is less than `n`, code is invalid. After `DUPN`, the stack height is incremented.
+   2. Before `SWAPN` if the current stack height is less than `n + 1`, code is invalid. After `SWAPN`, the stack height is unchanged.
+   3. Before `EXCHANGE` if the current stack height is less than `n + m + 1`, code is invalid. After `EXCHANGE`, the stack height is unchanged.
+4. Execution rules:
+   1. `DUPN`: the `n`'th stack item is duplicated at the top of the stack. (*Note: We use 1-based indexing here.*)
+   2. `SWAPN`: the `n + 1`'th stack item is swapped with the top of the stack.
+   3  `EXCHANGE`: the `n + 1`'th stack item is swapped with the `n + m + 1`'th stack item.
 
 The gas cost for all three instructions is set at 3.
 
@@ -88,14 +85,14 @@ This has no effect on backwards compatibility because the opcodes were not previ
 
 Given `stack[]` is a 0-based data structure, and `n`, `m` and `imm` are defined as according to the spec:
 
-    - `DUPN imm` to fail validation if `stack_height < n`.
-    - `SWAPN imm` to fail validation if `stack_height < n + 1`.
-    - `EXCHANGE imm` to fail validation if `stack_height < n + m + 1`.
-    - `DUPN imm` to increment maximum stack height of a function. Validation fails if maximum stack height exceeds limit of 1023.
-    - `DUPN imm`, `SWAPN imm`, and `EXCHANGE imm` to fail at run-time if gas available is less than 3.
-    - `DUPN imm` should duplicate the `stack[n - 1]` item and push it to the stack
-    - `SWAPN imm` should swap `stack[n]` with `stack[stack.top()]`
-    - `EXCHANGE imm` should swap `stack[n]` with `stack[n + m]`.
+- `DUPN imm` to fail validation if `stack_height < n`.
+- `SWAPN imm` to fail validation if `stack_height < n + 1`.
+- `EXCHANGE imm` to fail validation if `stack_height < n + m + 1`.
+- `DUPN imm` to increment maximum stack height of a function. Validation fails if maximum stack height exceeds limit of 1023.
+- `DUPN imm`, `SWAPN imm`, and `EXCHANGE imm` to fail at run-time if gas available is less than 3.
+- `DUPN imm` should duplicate the `stack[n - 1]` item and push it to the stack
+- `SWAPN imm` should swap `stack[n]` with `stack[stack.top()]`
+- `EXCHANGE imm` should swap `stack[n]` with `stack[n + m]`.
 
 ## Security Considerations