Language: C++

//=Main Part==================================================================//
@inlinable
func main(_ args: [String]) -> Int32 {
  // Your code goes here
  let a = geti()
  print(a * (a * (a + 1) + 1))

  return 0
}

//=Utilities for Programming Contests=========================================//
import Foundation
import os
// input
@discardableResult
@inlinable @inline(__always) func gets() -> String { readLine()! }
@inlinable @inline(__always) func geti() -> Int    { Int(gets())! }
@inlinable @inline(__always) func getd() -> Double { Double(gets())! }
// array
@inlinable @inline(__always) func getsA(_ c: Character = " ") -> [String] { gets().split(separator: c).map(String.init) }
@inlinable @inline(__always) func getiA(_ c: Character = " ") -> [Int]    { gets().split(separator: c).map{ Int(String.init($0))! } }
@inlinable @inline(__always) func getdA(_ c: Character = " ") -> [Double] { gets().split(separator: c).map{ Double(String.init($0))! } }
// structured bindings: splat
prefix operator *
@inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E)       { (a[0], a[1]) }
@inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E)    { (a[0], a[1], a[2]) }
@inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E, E) { (a[0], a[1], a[2], a[3]) }

//=Execution==================================================================//
os.exit(main(CommandLine.arguments))


Compiler output:
a.cc:2:1: error: stray '@' in program
    2 | @inlinable
      | ^
a.cc:15:1: error: stray '@' in program
   15 | @discardableResult
      | ^
a.cc:16:1: error: stray '@' in program
   16 | @inlinable @inline(__always) func gets() -> String { readLine()! }
      | ^
a.cc:16:12: error: stray '@' in program
   16 | @inlinable @inline(__always) func gets() -> String { readLine()! }
      |            ^
a.cc:17:1: error: stray '@' in program
   17 | @inlinable @inline(__always) func geti() -> Int    { Int(gets())! }
      | ^
a.cc:17:12: error: stray '@' in program
   17 | @inlinable @inline(__always) func geti() -> Int    { Int(gets())! }
      |            ^
a.cc:18:1: error: stray '@' in program
   18 | @inlinable @inline(__always) func getd() -> Double { Double(gets())! }
      | ^
a.cc:18:12: error: stray '@' in program
   18 | @inlinable @inline(__always) func getd() -> Double { Double(gets())! }
      |            ^
a.cc:20:1: error: stray '@' in program
   20 | @inlinable @inline(__always) func getsA(_ c: Character = " ") -> [String] { gets().split(separator: c).map(String.init) }
      | ^
a.cc:20:12: error: stray '@' in program
   20 | @inlinable @inline(__always) func getsA(_ c: Character = " ") -> [String] { gets().split(separator: c).map(String.init) }
      |            ^
a.cc:21:1: error: stray '@' in program
   21 | @inlinable @inline(__always) func getiA(_ c: Character = " ") -> [Int]    { gets().split(separator: c).map{ Int(String.init($0))! } }
      | ^
a.cc:21:12: error: stray '@' in program
   21 | @inlinable @inline(__always) func getiA(_ c: Character = " ") -> [Int]    { gets().split(separator: c).map{ Int(String.init($0))! } }
      |            ^
a.cc:22:1: error: stray '@' in program
   22 | @inlinable @inline(__always) func getdA(_ c: Character = " ") -> [Double] { gets().split(separator: c).map{ Double(String.init($0))! } }
      | ^
a.cc:22:12: error: stray '@' in program
   22 | @inlinable @inline(__always) func getdA(_ c: Character = " ") -> [Double] { gets().split(separator: c).map{ Double(String.init($0))! } }
      |            ^
a.cc:25:1: error: stray '@' in program
   25 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E)       { (a[0], a[1]) }
      | ^
a.cc:25:12: error: stray '@' in program
   25 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E)       { (a[0], a[1]) }
      |            ^
a.cc:26:1: error: stray '@' in program
   26 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E)    { (a[0], a[1], a[2]) }
      | ^
a.cc:26:12: error: stray '@' in program
   26 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E)    { (a[0], a[1], a[2]) }
      |            ^
a.cc:27:1: error: stray '@' in program
   27 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E, E) { (a[0], a[1], a[2], a[3]) }
      | ^
a.cc:27:12: error: stray '@' in program
   27 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E, E) { (a[0], a[1], a[2], a[3]) }
      |            ^
a.cc:2:2: error: 'inlinable' does not name a type; did you mean 'inline'?
    2 | @inlinable
      |  ^~~~~~~~~
      |  inline
a.cc:12:1: error: 'import' does not name a type
   12 | import Foundation
      | ^~~~~~
a.cc:12:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:17:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   17 | @inlinable @inline(__always) func geti() -> Int    { Int(gets())! }
      |  ^~~~~~~~~
      |  inline
a.cc:18:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   18 | @inlinable @inline(__always) func getd() -> Double { Double(gets())! }
      |  ^~~~~~~~~
      |  inline
a.cc:20:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   20 | @inlinable @inline(__always) func getsA(_ c: Character = " ") -> [String] { gets().split(separator: c).map(String.init) }
      |  ^~~~~~~~~
      |  inline
a.cc:21:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   21 | @inlinable @inline(__always) func getiA(_ c: Character = " ") -> [Int]    { gets().split(separator: c).map{ Int(String.init($0))! } }
      |  ^~~~~~~~~
      |  inline
a.cc:22:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   22 | @inlinable @inline(__always) func getdA(_ c: Character = " ") -> [Double] { gets().split(separator: c).map{ Double(String.init($0))! } }
      |  ^~~~~~~~~
      |  inline
a.cc:24:1: error: 'prefix' does not name a type
   24 | prefix operator *
      | ^~~~~~
a.cc:26:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   26 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E)    { (a[0], a[1], a[2]) }
      |  ^~~~~~~~~
      |  inline
a.cc:27:2: error: 'inlinable' does not name a type; did you mean 'inline'?
   27 | @inlinable @inline(__always) prefix func * <E> (a: [E]) -> (E, E, E, E) { (a[0], a[1], a[2], a[3]) }
      |  ^~~~~~~~~
      |  inline
a.cc:30:1: error: 'os' does not name a type
   30 | os.exit(main(CommandLine.arguments))
      | ^~