user: What is the c source code of the assembly code 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    L44
L49:
  mov    0x4(%rsp),%eax
  movl   $0x0,0x14(%rsp)
  sub    $0x1,%eax
  mov    %eax,0x8(%rsp)
  cmp    $0x1,%eax
  je     L219
L76:
  mov    0x8(%rsp),%eax
  movl   $0x0,0x18(%rsp)
  sub    $0x1,%eax
  mov    %eax,%r11d
  cmp    $0x1,%eax
  je     L135
L94:
  lea    -0x1(%r11),%eax
  movl   $0x0,0x1c(%rsp)
  cmp    $0x1,%eax
  je     L206
  mov    %r11d,0x20(%rsp)
  mov    %eax,%r11d
L16:
  xor    %ecx,%ecx
  lea    -0x1(%r11),%r12d
  mov    %ecx,%r15d
  cmp    $0x1,%r12d
  je     L28
L29:
  lea    -0x1(%r12),%ebx
  xor    %edx,%edx
  cmp    $0x1,%ebx
  je     L25
L36:
  cmp    $0x2,%ebx
  je     L117
  lea    -0x3(%rbx),%r13d
  lea    -0x6(%rbx),%esi
  xor    %r8d,%r8d
  mov    %r13d,%eax
  lea    -0x4(%rbx),%r9d
  and    $0xfffffffe,%eax
  sub    %eax,%esi
L102:
  lea    0x2(%r9),%ebp
  xor    %ecx,%ecx
  cmp    $0xffffffff,%r9d
  je     L193
L54:
  lea    -0x1(%rbp),%r14d
  xor    %r10d,%r10d
  cmp    $0x1,%r14d
  je     L42
L208:
  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     L208
  lea    -0x3(%rbp),%eax
  and    $0x1,%eax
  add    %r10d,%eax
L145:
  sub    $0x2,%ebp
  add    %eax,%ecx
  cmp    $0x1,%ebp
  jg     L54
  mov    %r9d,%ebp
  and    $0x1,%ebp
  add    %ecx,%ebp
L193:
  sub    $0x2,%r9d
  add    %ebp,%r8d
  cmp    %r9d,%esi
  jne    L102
  and    $0x1,%r13d
  lea    0x0(%r13,%r8,1),%eax
L228:
  sub    $0x2,%ebx
  add    %eax,%edx
  cmp    $0x1,%ebx
  jg     L36
  lea    -0x3(%r12),%eax
  and    $0x1,%eax
  add    %edx,%eax
L114:
  sub    $0x2,%r12d
  add    %eax,%r15d
  cmp    $0x1,%r12d
  jg     L29
  lea    -0x3(%r11),%eax
  and    $0x1,%eax
  add    %r15d,%eax
L154:
  sub    $0x2,%r11d
  add    %eax,0x1c(%rsp)
  cmp    $0x1,%r11d
  jg     L16
  mov    0x20(%rsp),%r11d
  lea    -0x3(%r11),%eax
  and    $0x1,%eax
  add    0x1c(%rsp),%eax
L206:
  sub    $0x2,%r11d
  add    %eax,0x18(%rsp)
  cmp    $0x1,%r11d
  jg     L94
  mov    0x8(%rsp),%eax
  sub    $0x3,%eax
  and    $0x1,%eax
  add    0x18(%rsp),%eax
L190:
  subl   $0x2,0x8(%rsp)
  mov    0x8(%rsp),%edi
  add    %eax,0x14(%rsp)
  cmp    $0x1,%edi
  jg     L76
  mov    0x4(%rsp),%eax
  sub    $0x3,%eax
  and    $0x1,%eax
  add    0x14(%rsp),%eax
L219:
  subl   $0x2,0x4(%rsp)
  mov    0x4(%rsp),%edi
  add    %eax,0x10(%rsp)
  cmp    $0x1,%edi
  jg     L49
  mov    0xc(%rsp),%eax
  and    $0x1,%eax
  add    0x10(%rsp),%eax
  mov    %eax,0xc(%rsp)
L44:
  mov    0xc(%rsp),%eax
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L117:
  mov    $0x1,%eax
  jmp    L228
  nopw   0x0(%rax,%rax,1)
L42:
  mov    $0x1,%eax
  jmp    L145
L25:
  mov    $0x1,%eax
  jmp    L114
L28:
  mov    $0x1,%eax
  jmp    L154
L135:
  mov    $0x1,%eax
  jmp    L190
```

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);
  }
}
```