#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
int /*<<< orphan*/ printf(char *, int);
int /*<<< orphan*/ scanf(char *, int *);
int main() {
  int N, Pi, once;
  scanf("%d", &N);
  once = 0;
  while (N--) {
    scanf("%d", &Pi);
    once = once ^ Pi;
  }
  printf("%d\n", once);
  return 0;
}


x86 assembly (clang, -O0):
<main>:
push   %rbp
mov    %rsp,%rbp
sub    $0x10,%rsp
movl   $0x0,-0x4(%rbp)
lea    0xeca(%rip),%rdi
lea    -0x8(%rbp),%rsi
call   1040 <scanf@plt>
movl   $0x0,-0x10(%rbp)
mov    -0x8(%rbp),%eax
mov    %eax,%ecx
add    $0xffffffff,%ecx
mov    %ecx,-0x8(%rbp)
cmp    $0x0,%eax
je     1178 <main+0x58>
lea    0xe9f(%rip),%rdi
lea    -0xc(%rbp),%rsi
call   1040 <scanf@plt>
mov    -0x10(%rbp),%eax
xor    -0xc(%rbp),%eax
mov    %eax,-0x10(%rbp)
jmp    1146 <main+0x26>
mov    -0x10(%rbp),%esi
lea    0xe81(%rip),%rdi
call   1030 <printf@plt>
xor    %eax,%eax
add    $0x10,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<main>:
push   %r15
push   %r14
push   %rbx
sub    $0x10,%rsp
lea    0xed0(%rip),%rdi
lea    0x8(%rsp),%rsi
call   1040 <scanf@plt>
xor    %ebx,%ebx
subl   $0x1,0x8(%rsp)
jb     1176 <main+0x56>
xor    %ebx,%ebx
lea    0xeb4(%rip),%r14
lea    0xc(%rsp),%r15
cs nopw 0x0(%rax,%rax,1)
nopl   0x0(%rax,%rax,1)
mov    %r14,%rdi
mov    %r15,%rsi
call   1040 <scanf@plt>
xor    0xc(%rsp),%ebx
subl   $0x1,0x8(%rsp)
jae    1160 <main+0x40>
lea    0xe86(%rip),%rdi
mov    %ebx,%esi
call   1030 <printf@plt>
xor    %eax,%eax
add    $0x10,%rsp
pop    %rbx
pop    %r14
pop    %r15
ret

LLVM IR (-O0):
@.str = [3 x i8] c"%d\00"
@.str.1 = [4 x i8] c"%d\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = alloca i32
%4 = alloca i32
store i32 0, i32* %1
%5 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32* %2)
store i32 0, i32* %4
br label %6
6: ; preds = %10, %0
%7 = load i32, i32* %2
%8 = add nsw i32 %7, -1
store i32 %8, i32* %2
%9 = icmp ne i32 %7, 0
br i1 %9, label %10, label %15
10: ; preds = %6
%11 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32* %3)
%12 = load i32, i32* %4
%13 = load i32, i32* %3
%14 = xor i32 %12, %13
store i32 %14, i32* %4
br label %6
15: ; preds = %6
%16 = load i32, i32* %4
%17 = call i32 @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i32 %16)
ret i32 0
}

LLVM IR (-O2):
@.str = [3 x i8] c"%d\00"
@.str.1 = [4 x i8] c"%d\0A\00"
define i32 @main() {
%1 = alloca i32
%2 = alloca i32
%3 = bitcast i32* %1 to i8*
%4 = bitcast i32* %2 to i8*
%5 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32* %1)
%6 = load i32, i32* %1
%7 = add nsw i32 %6, -1
store i32 %7, i32* %1
%8 = icmp eq i32 %6, 0
br i1 %8, label %17, label %9
9: ; preds = %0, %9
%10 = phi i32 [ %13, %9 ], [ 0, %0 ]
%11 = call i32 @scanf(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @.str, i64 0, i64 0), i32* %2)
%12 = load i32, i32* %2
%13 = xor i32 %12, %10
%14 = load i32, i32* %1
%15 = add nsw i32 %14, -1
store i32 %15, i32* %1
%16 = icmp eq i32 %14, 0
br i1 %16, label %17, label %9
17: ; preds = %9, %0
%18 = phi i32 [ 0, %0 ], [ %13, %9 ]
%19 = call i32 @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i32 %18)
ret i32 0
}