[51nod p2106] an odd number of times [bit operation]

$link$

analysis ：

Exclusive or
A number occurs an even number of times Their XOR value is $0$ Otherwise, this number

CODE：

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define reg register
using namespace std;
typedef long long ll;
int n,x,ans; 
int main(){
    
	scanf("%d",&n);
	while(n--)
	{
    
		scanf("%d",&x);
		ans^=x;
	}
	printf("%d",ans);
	return 0;
}