user: What would the C source look like for the assembly code provided here:

```asm
<reverseOnlyLetters>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x30,%rsp
  mov    %rdi,-0x28(%rbp)
  mov    -0x28(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    %eax,-0x14(%rbp)
  mov    -0x14(%rbp),%eax
  add    $0x1,%eax
  mov    $0x1,%esi
  mov    %eax,%edi
  call   <calloc@plt>
  mov    %rax,-0x8(%rbp)
  mov    -0x14(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x8(%rbp),%rax
  add    %rdx,%rax
  movb   $0x0,(%rax)
  movl   $0x0,-0x1c(%rbp)
  mov    -0x14(%rbp),%eax
  sub    $0x1,%eax
  mov    %eax,-0x18(%rbp)
  movl   $0x0,-0x10(%rbp)
  movl   $0x0,-0xc(%rbp)
  jmp    L94
L51:
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x60,%al
  jle    L76
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x7a,%al
  jle    L74
L76:
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x40,%al
  jle    L142
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x5a,%al
  jg     L142
L74:
  mov    $0x1,%eax
  jmp    L133
L142:
  mov    $0x0,%eax
L133:
  mov    %eax,-0x10(%rbp)
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x60,%al
  jle    L34
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x7a,%al
  jle    L119
L34:
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x40,%al
  jle    L30
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x5a,%al
  jg     L30
L119:
  mov    $0x1,%eax
  jmp    L140
L30:
  mov    $0x0,%eax
L140:
  mov    %eax,-0xc(%rbp)
  cmpl   $0x0,-0x10(%rbp)
  je     L0
  cmpl   $0x0,-0xc(%rbp)
  je     L0
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    -0x18(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x8(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rax),%eax
  mov    %al,(%rdx)
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    -0x1c(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x8(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rax),%eax
  mov    %al,(%rdx)
  addl   $0x1,-0x1c(%rbp)
  subl   $0x1,-0x18(%rbp)
  jmp    L94
L0:
  cmpl   $0x0,-0x10(%rbp)
  jne    L59
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    -0x1c(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x8(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rax),%eax
  mov    %al,(%rdx)
  addl   $0x1,-0x1c(%rbp)
L59:
  cmpl   $0x0,-0xc(%rbp)
  jne    L94
  mov    -0x18(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    -0x18(%rbp),%edx
  movslq %edx,%rcx
  mov    -0x8(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rax),%eax
  mov    %al,(%rdx)
  subl   $0x1,-0x18(%rbp)
L94:
  mov    -0x1c(%rbp),%eax
  cmp    -0x18(%rbp),%eax
  jle    L51
  mov    -0x8(%rbp),%rax
  leave
  ret
```

assistant: ```c
char *reverseOnlyLetters(char *S) {
  int size = strlen(S);
  char *newStr = calloc(size + 1, sizeof(char));
  newStr[size] = 0;
  int l = 0, r = size - 1;
  int isL = 0, isR = 0;
  while (l <= r) {
    isL = ((S[l] >= 'a' && S[l] <= 'z') || (S[l] >= 'A' && S[l] <= 'Z'));
    isR = ((S[r] >= 'a' && S[r] <= 'z') || (S[r] >= 'A' && S[r] <= 'Z'));
    if (isL && isR) {
      newStr[r] = S[l];
      newStr[l] = S[r];
      l++;
      r--;
    } else {
      if (!isL) {
        newStr[l] = S[l];
        l++;
      }
      if (!isR) {
        newStr[r] = S[r];
        r--;
      }
    }
  }
  return newStr;
}
```