user: Please show me the C implementation that matches the assembly code listed below:

```asm
<fib_serial>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %edi,0xc(%rsp)
  mov    %edi,0x4(%rsp)
  movl   $0x0,0x10(%rsp)
  cmp    $0x1,%edi
  jle    L12
L43:
  mov    0x4(%rsp),%eax
  movl   $0x0,0x14(%rsp)
  sub    $0x1,%eax
  mov    %eax,0x8(%rsp)
  cmp    $0x1,%eax
  je     L152
L105:
  mov    0x8(%rsp),%eax
  movl   $0x0,0x18(%rsp)
  sub    $0x1,%eax
  mov    %eax,%r11d
  cmp    $0x1,%eax
  je     L193
L96:
  lea    -0x1(%r11),%eax
  movl   $0x0,0x1c(%rsp)
  cmp    $0x1,%eax
  je     L160
  mov    %r11d,0x20(%rsp)
  mov    %eax,%r11d
L48:
  xor    %ecx,%ecx
  lea    -0x1(%r11),%r12d
  mov    %ecx,%r15d
  cmp    $0x1,%r12d
  je     L117
L221:
  lea    -0x1(%r12),%ebx
  xor    %edx,%edx
  cmp    $0x1,%ebx
  je     L53
L0:
  cmp    $0x2,%ebx
  je     L77
  lea    -0x3(%rbx),%r13d
  lea    -0x6(%rbx),%esi
  xor    %r8d,%r8d
  mov    %r13d,%eax
  lea    -0x4(%rbx),%r9d
  and    $0xfffffffe,%eax
  sub    %eax,%esi
L138:
  lea    0x2(%r9),%ebp
  xor    %ecx,%ecx
  cmp    $0xffffffff,%r9d
  je     L195
L161:
  lea    -0x1(%rbp),%r14d
  xor    %r10d,%r10d
  cmp    $0x1,%r14d
  je     L217
L102:
  lea    -0x1(%r14),%edi
  mov    %r9d,0x3c(%rsp)
  sub    $0x2,%r14d
  mov    %esi,0x38(%rsp)
  mov    %r10d,0x34(%rsp)
  mov    %ecx,0x30(%rsp)
  mov    %r8d,0x2c(%rsp)
  mov    %edx,0x28(%rsp)
  mov    %r11d,0x24(%rsp)
  call   <fib_serial>
  mov    0x34(%rsp),%r10d
  mov    0x24(%rsp),%r11d
  mov    0x28(%rsp),%edx
  mov    0x2c(%rsp),%r8d
  add    %eax,%r10d
  cmp    $0x1,%r14d
  mov    0x30(%rsp),%ecx
  mov    0x38(%rsp),%esi
  mov    0x3c(%rsp),%r9d
  jg     L102
  lea    -0x3(%rbp),%eax
  and    $0x1,%eax
  add    %r10d,%eax
L73:
  sub    $0x2,%ebp
  add    %eax,%ecx
  cmp    $0x1,%ebp
  jg     L161
  mov    %r9d,%ebp
  and    $0x1,%ebp
  add    %ecx,%ebp
L195:
  sub    $0x2,%r9d
  add    %ebp,%r8d
  cmp    %r9d,%esi
  jne    L138
  and    $0x1,%r13d
  lea    0x0(%r13,%r8,1),%eax
L56:
  sub    $0x2,%ebx
  add    %eax,%edx
  cmp    $0x1,%ebx
  jg     L0
  lea    -0x3(%r12),%eax
  and    $0x1,%eax
  add    %edx,%eax
L158:
  sub    $0x2,%r12d
  add    %eax,%r15d
  cmp    $0x1,%r12d
  jg     L221
  lea    -0x3(%r11),%eax
  and    $0x1,%eax
  add    %r15d,%eax
L4:
  sub    $0x2,%r11d
  add    %eax,0x1c(%rsp)
  cmp    $0x1,%r11d
  jg     L48
  mov    0x20(%rsp),%r11d
  lea    -0x3(%r11),%eax
  and    $0x1,%eax
  add    0x1c(%rsp),%eax
L160:
  sub    $0x2,%r11d
  add    %eax,0x18(%rsp)
  cmp    $0x1,%r11d
  jg     L96
  mov    0x8(%rsp),%eax
  sub    $0x3,%eax
  and    $0x1,%eax
  add    0x18(%rsp),%eax
L198:
  subl   $0x2,0x8(%rsp)
  mov    0x8(%rsp),%edi
  add    %eax,0x14(%rsp)
  cmp    $0x1,%edi
  jg     L105
  mov    0x4(%rsp),%eax
  sub    $0x3,%eax
  and    $0x1,%eax
  add    0x14(%rsp),%eax
L152:
  subl   $0x2,0x4(%rsp)
  mov    0x4(%rsp),%edi
  add    %eax,0x10(%rsp)
  cmp    $0x1,%edi
  jg     L43
  mov    0xc(%rsp),%eax
  and    $0x1,%eax
  add    0x10(%rsp),%eax
  mov    %eax,0xc(%rsp)
L12:
  mov    0xc(%rsp),%eax
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L77:
  mov    $0x1,%eax
  jmp    L56
  nopw   0x0(%rax,%rax,1)
L217:
  mov    $0x1,%eax
  jmp    L73
L53:
  mov    $0x1,%eax
  jmp    L158
L117:
  mov    $0x1,%eax
  jmp    L4
L193:
  mov    $0x1,%eax
  jmp    L198
```

assistant: ```c
int fib_serial(int n) {
  int x = 0, y = 0;
  if (n < 2)
    return n;
  else {
    x = fib_serial(n - 1);
    y = fib_serial(n - 2);
    return (x + y);
  }
}
```